ILLUSTRATIONS AND ADDITIONS.

[71]. p. 210—“On the Chimborazo, upwards of eight thousand feet higher than Etna.”

Small singing birds, and even butterflies, (as I have myself witnessed in the Pacific,) are often met with at great distances from the shore, during storms blowing off land. In a similar manner insects are involuntarily carried into the higher regions of the atmosphere, to an elevation of 17,000 to 19,000 feet above the plains. The light bodies of these insects are borne upwards by the vertically ascending currents of air caused by the heated condition of the earth’s surface. M. Boussingault, an admirable chemist, who ascended the Gneiss Mountains of Caracas, while holding the appointment of Professor in the newly established Mining Academy at Santa Fé de Bogotá, witnessed, during his ascent to the summit of the Silla, a phenomenon which confirmed in a most remarkable manner this vertical ascent of air. He and his companion, Don Mariano de Rivero, observed at noon a number of luminous whitish bodies rise from the valley of Caracas to the summit of the Silla, an elevation of 5755 feet, and then sink towards the adjacent sea coast. This phenomenon was uninterruptedly prolonged for a whole hour, when it was discovered that the bodies, at first mistaken for a flock of small birds, were a number of minute balls of grass-haums. Boussingault sent me some of this grass, which was immediately recognised by Professor Kunth as a species of Vilfa, a genus of grass which together with Agrostis is of frequent occurrence in the provinces of Caracas and Cumana. It was the Vilfa tenacissima of our Synopsis Plantarum æquinoctialium Orbis Novi, t. i. p. 205. Saussure found butterflies on Mont Blanc, and Ramond observed them in the solitudes around the summit of Mont Perdu. When MM. Bonpland, Carlos Montufar, and myself, on the 23rd of June, 1802, ascended the eastern declivity of Mount Chimborazo, to a height of 19,286 feet, and where the barometer had fallen to 14·84 inches, we found winged insects buzzing around us. We recognised them to be Diptera, resembling flies, but it was impossible to catch these insects standing on the rocky ledges (cuchilla), often less than a foot in breadth, and between masses of snow precipitated from above. The elevation at which we observed these insects was almost the same as that in which the naked trachytic rock, which projected from the eternal snows around, exhibited the last traces of vegetation in Lecidea geographica. These insects were flying at an elevation of 18,225 feet, or nearly 2660 feet higher than the summit of Mont Blanc: and somewhat below this height, at an elevation of 16,626 feet, and therefore also above the region of snow, M. Bonpland saw yellow butterflies flying close to the ground. The mammalia which live nearest to the region of perpetual snow, are, in the Swiss Alps, the hybernating marmot, and a very small field-mouse, (Hypudæus nivalis,) described by Martius, which on the Faulhorn lays up, almost under the snow, a store of the roots of phanerogamic alpine plants.[^[JC]] The opinion prevalent in Europe, that the beautiful rodent, the Chinchilla, whose soft and glossy fur is so much esteemed, is found in the highest mountain regions of Chili, is an error. The Chinchilla laniger (Gray) lives only in a mild lower zone, and does not advance further south than the parallel of 35°.[^[JD]]

Whilst among our European Alps, Lecideas, Parmelias, and Umbilicarias but scantily clothe with a few coloured patches those rocks that are not wholly covered with snow, we found in the Andes, at elevations of 13,700 to nearly 15,000 feet, some phanerogamic plants which we were the first to describe; as for instance, the woolly species of Fraylejon. (Culcitium nivale, C. rufescens, and C. reflexum, Espeletia grandiflora, and E. argentea), Sida pichinchensis, Ranunculus nubigenus, R. Gusmanni with red or orange-coloured flowers, the small moss-like umbelliferous plant, Myrrhis andicola, and Fragosa arctioides. On the declivity of the Chimborazo, the Saxifraga Boussingaulti, described by Adolph Brongniart, grows beyond the limits of perpetual snow on loose blocks of stone at an elevation of 15,770 feet above the level of the sea, and not at 17,000 as has been stated in two admirable English journals.[^[JE]] This Saxifrage, discovered by Boussingault, must therefore be regarded as the highest growing phanerogamic plant in the world.

The vertical height of Chimborazo is, according to my measurement, 21,422 feet.[^[JF]] This result is a mean between those which have been given by the French and Spanish Academicians. The principal differences do not here depend on different assumptions for the refraction, but on a difference in reducing the measured line to the level of the sea. This reduction can only be made in the Andes by the barometer, and hence every so-called trigonometric measurement must also necessarily be a barometric one, whose result will vary according to the different formulæ employed. Owing to the enormous mass of the mountain chain, we can only obtain very small angles of altitude, when the greater portion of the whole height has to be measured trigonometrically, and the observation is made at some low and distant point near the plain or the level of the sea. It is on the other hand extremely difficult to obtain a convenient base line, as the space that is to be determined barometrically increases with every step we advance towards the mountain. These obstacles have to be encountered by every traveller who on the high table-lands, which surround the summit of the Andes, selects a spot for performing a geodetic operation. On the pumice-covered plain of Tapia, to the west of the Rio Chambo, at a height of 9477 feet, barometrically determined, I measured the Chimborazo. The Llanos de Luisa, and more especially the plain of Sisgun, whose elevation is 12,150 feet, would yield greater angles of altitude. I had on one occasion made every preparation necessary for the measurement of Mount Chimborazo, from the plain of Sisgun, when the summit of the mountain was suddenly shrouded in a dense cloud.

Some hypothetical suggestions, regarding the probable derivation of the name of the far-famed “Chimborazo,” may not be wholly unwelcome to etymologists. The district in which the mountain is situated is called Chimbo, a word which La Condamine [^[JG]] derives from chimpani, to cross a river. “Chimboraço” means, according to him, “the snow of the opposite bank,” from the fact of a brook being crossed at the village of Chimbo, in sight of the huge snow-covered mountain. (In the Quichua language chimpa signifies the opposite bank or side; chimpani to cross a river, bridge, &c.) Several natives of the province of Quito assured me that Chimborazo meant simply the snow of Chimbo. In Carguairazo we meet with the same termination, and it would appear that “razo” is a provincial word. The Jesuit Holguin, whose excellent vocabulary [^[JH]] I possess, is not acquainted with the word razo. The genuine term for snow is ritti. On the other hand, my friend, Professor Buschmann, an admirable linguist, remarks that in the Chinchaysuyo dialect, (employed north of Cuzco as far as Quito and Pasto) raju, the j being apparently guttural, signifies snow.[^[JI]] As chimpa and chimpani do not well suit on account of the a, we may seek a definite meaning for the first portion of the name of the mountain and of the village Chimbo, in the Quichua word “chimpu,” which is used to express a coloured thread or fringe (señal de lana, hilo ó borlilla de colores); the redness of the sky (arreboles), and the halo round the sun and moon. The name of the mountain might be thus derived from this word, without reference to the district or village. At all events, whatever may be the etymology of the word Chimborazo, it should be written in the Peruvian manner Chimporazo, as the Peruvians have no b in their alphabet.

May not the name of this colossal mountain be wholly independent of the Inca language, and have come down from a bygone age? The Inca or Quichua language had not been introduced long prior to the Spanish invasion into the kingdom of Quito, where the now wholly extinct Puruay language had been previously used. The names of other mountains, as Pichincha, Ilinissa, and Cotopaxi, are wholly devoid of meaning in the language of the Incas, and are therefore undoubtedly of higher antiquity than the introduction of the worship of the sun, and of the court-language of the rulers of Cuzco. The names of mountains and rivers belong in all regions of the earth to the most ancient and authentic relics of languages; and my brother, Wilhelm von Humboldt, in his investigations into the former distribution of the Iberian races, has made ingenious use of these names. A singular and unexpected statement has recently been made,[^[JJ]] “that the Incas, Tupac Yupanqui, and Huayna Capac, were astonished on their first conquest of Quito, to find a dialect of their Quichua language in use among the natives.” Prescott, however, seems to regard this as a very bold assertion.[^[JK]]

If we could suppose the pass of St. Gothard, Mount Athos, or the Rigi, piled on the summit of the Chimborazo, we should have the elevation which is at present ascribed to the Dhawalagiri in the Himalaya. The geologist who regards the interior of our planet from a more general point of view, and to whom not the directions, but the relative heights of the rocky projections, which we designate mountain chains, appear but as phenomena of little importance, will not be astonished if at some future period mountain summits should be discovered between the Himalaya and the Altai, which should surpass in height those of Dhawalagiri and Djawahir as much as these exceed that of Chimborazo.[^[JL]] The great height to which the snow-line recedes in summer on the northern declivity of the Himalaya, owing to the heat radiated from the elevated plateaux in Central Asia, renders the mountain, notwithstanding that it is situated in 29 to 30½° north lat., as accessible as are the Peruvian Andes in the region of the tropics. Captain Gerard has moreover recently ascended the Tarhigang as high, if not 117 feet higher,[^[JM]] than I ascended the Chimborazo. Unfortunately, as I have elsewhere more fully shown, these mountain ascents, beyond the line of perpetual snow, however they may engage the curiosity of the public, are of very little scientific utility.

[72]. p. 210—“The Condor, that giant among vultures.”

I have elsewhere [^[JN]] given the natural history of the Condor, which before my travels had been variously misstated. The name is properly Cuntur in the Inca language; Mañque among the Araucanes in Chili; Sarcoramphus Condor according to Duméril. I sketched the head of this bird from life, of the natural size, and had my drawing engraved. Next to the Condor, the Lämmergeier of Switzerland, and the Falco destructor (Daud.), probably Linnæus’ Falco Harpyia, are the largest of all flying birds.

The region which may be regarded as the common resort of the Condor, begins at the elevation of Mount Etna. It embraces atmospheric strata which are from 10,000 to 19,000 feet above the level of the sea. Humming birds also, which in their summer flights advance as far as 61° north lat. on the western coast of America, and are on the other hand found in the Archipelago of the Tierra del Fuego, were seen by Von Tschudi in Puna at an elevation of 14,600 feet.[^[JO]] There is a pleasure in comparing the largest and the smallest of the feathered inhabitants of the air. The largest among the Condors found in the Cordilleras, near Quito, measure nearly 15 feet across the expanded wings, and the smaller ones 8½ feet. This size, and the visual angle at which the birds are seen vertically above one’s head, afford an idea of the enormous height to which the Condor soars in a clear sky. A visual angle of four minutes, for instance, would give a vertical elevation of 7330 feet. The cavern (Mackay) of Antisana, opposite the mountain of Chussulongo, and where we measured the birds soaring over the chain of the Andes, lies at an elevation of nearly 16,000 feet above the surface of the Pacific; the absolute height which the Condor reached must therefore be 23,273 feet, a height at which the barometer scarcely stands at 12·7 inches; but which, however, does not exceed that of the loftiest summit of the Himalaya. It is a remarkable physiological phenomenon that the same bird, which wheels for hours together through these highly rarefied regions, should be able suddenly, as for instance on the western declivity of the volcano of Pichincha, to descend to the sea-shore, and thus in the course of a few hours traverse, as it were, all climates. At heights of 23,000 feet and upwards the membranous air-sacs of the Condor must undergo a remarkable degree of inflation after being filled in lower regions of the atmosphere.

Ulloa, more than a hundred years ago, expressed his astonishment that the Vulture of the Andes could soar at heights where the pressure of the atmosphere was less than fifteen inches.[^[JP]] An opinion was at that time entertained, from the analogy of experiments made with the air-pump, that no animal could exist under this slight amount of atmospheric pressure. I have myself, as has already been mentioned, seen the barometer fall to 14·85 inches on the Chimborazo; and my friend, M. Gay-Lussac, breathed for a quarter of an hour an atmosphere in which the pressure was only 12·9 inches. It must be admitted that man, when wearied by muscular exertion, finds himself in a state of painful exhaustion at such elevations; but in the Condor, the respiratory process seems to be performed with equal facility under a pressure of 30 or of 13 inches. This bird probably raises itself voluntarily to a greater height from the surface of our earth than any other living creature. I use the expression “voluntarily,” since small insects and siliceous-shelled infusoria are frequently borne to greater elevations by a rising current of air. It is probable that the Condor flies even higher than the above calculations would appear to show. I remember observing near the Cotopaxi, in the pumice plain of Suniguaicu, at an elevation of 14,471 feet above the level of the sea, this bird soaring at such a height above my head that it appeared like a black speck. But what is the smallest angle under which faintly illumined objects can be distinguished? Their form (linear extension) exercises a great influence on the minimum of this angle. The transparency of the mountain air is so great under the equator, that in the province of Quito, as I have elsewhere stated, the white cloak (poncho) of a horseman may be distinguished with the naked eye at a horizontal distance of 89,664 feet, and therefore under an angle of thirteen seconds. It was my friend Bonpland whom we observed, from the pleasant country-seat of the Marques de Selvalegre, moving along a black rocky precipice on the volcano of Pichincha. Lightning conductors, being thin elongated objects, are visible, as Arago has observed, from the greatest distances and under the smallest angles.

The account I have given in my Monograph of the Condor (Zoologie, pp. 26–45) of the habits of this powerful bird in the mountain districts of Quito and Peru has been confirmed by a more recent traveller, Gay, who has explored the whole of Chili, and described it in his admirable work, Historia fisica y politica de Chile. This bird which, singularly enough, like the Lamas, Vicuñas, Alpacas and Guanacos, is not found beyond the equator in New Granada, penetrates as far south as the Straits of Magellan. In Chili, as in the elevated plateaux of Quito, the Condors, which usually live in pairs, or even alone, congregate in flocks for the purpose of attacking lambs and calves, or seizing on young Guanacos (Guanacillos). The havoc annually committed by the Condor among the herds of sheep, goats and cattle, as well as among the wild vicuñas, alpacas and guanacos of the chain of the Andes is very considerable. The Chilians assert that this bird when in captivity can endure hunger for forty days; when in a free state, however, its voracity is excessive, and it then, like the vulture, feeds by preference on carrion.

The mode of catching these birds, by an inclosure of palisades such as I have already described, is as successful in Chili as in Peru, for the bird after being rendered heavy from excess of food is obliged to run a short distance with half-extended wings before it can take flight. A dead ox which is already in an incipient state of decomposition, is strongly inclosed with palisades, within which narrow space the Condors throng together; being unable, as already observed, to fly on account of the excess of food which they have devoured, and impeded in their run by the palisades, these birds are either killed by the natives with clubs, or are caught alive by the lasso. The Condor was represented as a symbol of strength on the coinage of Chili immediately after the first declaration of political independence.[^[JQ]]

The different species of Gallinazos, which are much more considerable in point of numbers than the Condors, are also far more useful than the latter in the great economy of Nature for destroying and removing animal substances that are becoming decomposed, and thus purifying the atmosphere in the neighbourhood of human dwellings. In tropical America, I have sometimes seen seventy or eighty of these creatures collected round a dead ox; and I am able, as an eye-witness, to confirm the fact that has of late erroneously been called in question by ornithologists, that the appearance of one single king-vulture (who is not larger than the Gallinazos) is sufficient to put a whole assemblage of these birds to flight. No contest ever takes place; but the Gallinazos (two species of which, (Cathartes urubu and C. aura,) have been confounded together by an unfortunately fluctuating nomenclature) are intimidated by the sudden appearance and the courageous demeanour of the richly coloured “Sarcoramphus Papa.” As the ancient Egyptians protected the Percnopteri, which purified the atmosphere, so also the wanton destruction of Gallinazos is punished in Peru by a fine (multa) which, according to Gay, amounts in some cities to 300 piastres for every bird. It is a remarkable fact, that this species of vulture, as was already testified by Don Felix de Azara, if trained early, will so accustom themselves to the person who has reared them, that they will follow him on a journey for many miles, flying after his carriage across the Pampa.

[73]. p. 211—“Encloses their rotating bodies.”

Fontana, in his admirable treatise “on the poison of the viper,” vol. i. p. 62, mentions that he succeeded in restoring to animation, after two hours’ immersion in a drop of water, a wheel-animalcule which had lain in a dried and motionless condition for the space of two years and a half.[^[JR]]

The so-called reanimation of Rotifera has very recently again been made a subject of lively discussion, since observations have been conducted with more exactness and subjected to a stricter criticism. Baker affirmed that in 1771, he had revived paste-eels which Needham had given him in the year 1744! Franz Bauer saw his Vibrio tritici, which had lain four years in a dry state, move on being moistened. The remarkably careful and experienced observer, Doyère,[^[JS]] draws the following conclusions from his beautiful experiments: that Rotifera revive, i.e. pass from a motionless state to one of motion, after being exposed to a cold of 11°.2 Fahr., or to a heat of 113° Fahr.; that they preserve the property of reviving in dry sand up to a temperature of 159° Fahr.; but that they lose this property and remain immoveable if warmed in moist sand to 131° Fahr. only;[^[JT]] and that the possibility of this so-called revivification is not prevented by their being exposed to desiccation for twenty-eight days in barometric tubes, in vacuo, even should chloride of lime or sulphuric acid be employed.[^[JU]]

Doyère has also seen Rotifera slowly revive after being dried without sand, (desséchés à nu,) a fact which Spallanzani denies.[^[JV]] “Desiccation conducted in an ordinary temperature might be open to many objections which are not perhaps wholly obviated by the employment of a dry vacuum; but when we observe that the Tardigrades irrevocably perish in a temperature of 131° Fahr. if their tissues are permeated with water, whereas they can, when dried, support a temperature that may be estimated at 248° Fahr., we are disposed to admit that the sole condition required for animal revivification is the perfect integrity of organic structure and continuity.”

In like manner, the sporules, or germinating cells of cryptogamic plants, which Kunth compares to the propagation of certain phanerogamic plants by buds (bulbillæ), retain their power of germination in the highest temperature. According to the most recent experiments of Payen, the sporules of a small fungus (Oïdium aurantiacum), which invests the crumb of bread with a reddish feathery coating, do not even lose their vegetative powers by being exposed in closed tubes for half an hour to a temperature of 183° to 208° Fahr. before being strewn on fresh, unspoilt dough. May not the newly discovered and wonderful monad (Monas prodigiosa), which causes blood-like spots in mealy substances, have been mixed with this fungus?

Ehrenberg, in his great work on Infusoria (p. 492–496), has given the most complete history of all the observations instituted on the so-called revivification of Rotifera. He believes, that notwithstanding all the means of desiccation employed, the organization-fluid still remains in the apparently dead animal. He contests the hypothesis of “latent life”; for death, he says, “is not life in a torpid state, but the absence of life.”

The hybernation or winter-sleep of both warm and coldblooded animals, as dormice, marmots, sand-martins (Hirundo riparia, according to Cuvier)[^[JW]], and of frogs and toads, affords us evidence of the diminution, if not of the complete suspension, of the organic functions. Frogs awakened from their winter-sleep by warmth, can remain eight times longer under water, without drowning, than frogs in the breeding season. It seems as if the respiratory functions of the lungs require a less degree of activity after the long suspension of their excitability. The circumstance of the sand-martin burying itself during the winter in marshes, is a phenomenon which, while it scarcely admits of a doubt, is the more remarkable, because in birds, the function of respiration is so extremely energetic, that, according to Lavoisier’s experiments, two sparrows in an ordinary condition will, in the same time, decompose as much atmospheric air as a Guinea-pig.[^[JX]] Winter-sleep is not supposed to be general to the whole species of these sand-martins, but only to some few individuals.[^[JY]]

As in the frigid zone deprivation of warmth produces winter-sleep in some animals, so in the torrid regions, within the tropics, an analogous phenomenon is manifested that has not hitherto been sufficiently regarded, and to which I have applied the term summer-sleep.[^[JZ]] Drought and a continuous high temperature act like the cold of winter in reducing excitability. Madagascar, excepting a very small portion of its southern extremity, lies within the tropics, and here, as was already observed by Bruguière, the hedgehog-like Tenrecs (Centeres, Illiger), one species of which (C. ecaudatus) was introduced into the Isle of France (20° 9′, latitude), sleep during excessive heat. The objection advanced by Desjardins, that the time of their sleep falls within the season of winter in the southern hemisphere, can scarcely be regarded as applicable in reference to a country, where the mean temperature of the coldest month is nearly 7° Fahr. above that of the hottest month in Paris; and this circumstance cannot therefore change the three months’ summer-sleep of the Tenrec in Madagascar and Port Louis (Isle of France) into actual hybernation.

In a similar manner, the Crocodile in the Llanos of Venezuela, the land and water Tortoises on the Orinoco, and the colossal Boa, and many of the smaller species of serpents, lie torpid and motionless in the hardened ground, throughout the hot and dry season of the year. The missionary Gilij relates, that the natives, in seeking the dormant Terekai (land-tortoises), which lie buried in dry mud to the depth of 16 or 17 inches, are often bitten by serpents suddenly awakened, and which had buried themselves with the tortoises. An admirable observer, Dr. Peters, who has only just returned from the eastern coast of Africa, writes to me as follows: “I could not obtain any certain information regarding the Tenrec during my short stay in Madagascar, but I am, on the other hand, well aware, that in the portion of eastern Africa where I spent several years, different species of tortoises (Pentonyx and Trionices) remain enclosed for months together, without food, in the parched and indurated ground, during the dry season of this tropical country. The Lepidosiren also remains motionless and coiled up in the hardened earth, from May to December, wherever the swamps have been dried up.”

We thus meet with an enfeeblement of certain vital functions in numerous and very different classes of animals, and, what is peculiarly striking, without the same phenomenon presenting itself in organisms nearly allied, and belonging to one and the same family. The northern glutton (Gulo), allied to the badger (Meles), does not, like the latter, sleep during the winter; whilst, according to Cuvier, “a Myoxus (Dormouse of Senegal, Myoxus Coupeii) which had probably never experienced a winter-sleep in its tropical home, fell into a state of hybernation at the beginning of winter, the first year it was brought to Europe.” This enfeeblement of the vital functions and vital activity passes through several gradations, according as it extends to the processes of nutrition, respiration and muscular movement, or induces a depression of the cerebral and nervous systems. The winter-sleep of the solitary bear and of the badger is not attended with rigidity, and hence the awakening of these animals is easy, and, as I frequently heard in Siberia, very dangerous to the hunters and country people. The recognition of the gradation and connection of these phenomena leads us to the so-called vita minima of the microscopic organisms, which occasionally fall in the Atlantic in showers of meteoric dust, and some of which have green ovaries and are engaged in a self-generating process. The apparent revivification of the Rotifera and of the siliceous-shelled Infusoria is only the renewal of long enfeebled vital functions—a condition of vitality never entirely extinguished, but merely revived by excitation. Physiological phenomena can only be comprehended by being traced through the entire series of analogous modifications.

[74]. p. 211—“Winged Insects.”

The fructification of diœcious plants was at one time principally ascribed to the agency of the wind. It has been shown by Kölreuter, and also with much ingenuity by Sprengel, that bees, wasps and numerous small winged insects, are the main agents in this process. I use the phrase “main agents”, since I cannot regard it as consonant to nature that fructification should be impossible without the intervention of these insects, as Willdenow has also fully shewn.[^[KA]] On the other hand dichogamy, sap-marks, (maculæ indicantes), coloured spots indicating the presence of honey-vessels, and fructification by insects, appear to be almost inseparable from one another.[^[KB]]

The statement often repeated since Spallanzani, that the diœcious common hemp (Cannabis sativa), which was introduced into Europe from Persia, bears ripe seeds without being in the neighbourhood of pollen-tubes, has been entirely refuted by more recent investigations. When seeds have been obtained, anthers in a rudimentary state have been found near the ovarium, and these may have been capable of yielding some grains of fructifying pollen. Such hermaphrodism is frequent in the whole family of Urticeæ, but a singular and hitherto unexplained phenomenon is manifested in the forcing-houses at Kew by a small New Holland shrub, the Cœlebogyne of Smith. This phanerogamic plant brings forth seeds in England without exhibiting any trace of male organs, and without the bastard introduction of the pollen of any other plant. “A species of Euphorbiaceæ,” (?) writes the distinguished botanist, Jussieu, “the Cœlebogyne, which, although but recently described, has been cultivated for many years in English conservatories, has several times borne seeds, which were evidently perfect, since the well-formed embryos they contained have produced similar plants. The most careful observations have hitherto failed in discovering the slightest trace of anthers or even pollen in the flowers, which are diœcious. No male plants of this kind are known to exist in England. The embryo cannot therefore have come from the pollen, which is wholly deficient, but must have been formed entirely in the ovule.”[^[KC]]

In order to obtain a fresh and confirmatory explanation of this important and isolated physiological phenomenon, I lately addressed myself to my young friend, Dr. Joseph Hooker, who after having accompanied Sir James Ross in his Antarctic voyage, has now joined the great Thibeto-Himalayan expedition. Dr. Hooker wrote to me as follows from Alexandria, at the close of December, 1847, prior to his embarkation at Suez: “Our Cœlebogyne still flowers with my father at Kew, as well as in the Gardens of the Horticultural Society. It ripens its seeds regularly. I have repeatedly examined it with care, but have never been able to discover a penetration of pollen utricles into the stigma, nor any traces of their presence in the latter or in the style. In my herbarium the male blossoms are in small catkins.”

[75]. p. 212—“Like luminous stars.”

The phosphorescence of the ocean is one of those splendid phenomena of nature which excite our admiration, even when we behold its recurrence every night for months together. The ocean is phosphorescent in all zones of the earth, but he who has not witnessed the phenomenon in the tropics, and especially in the Pacific, can form but a very imperfect idea of the majesty of this brilliant spectacle. The traveller on board a man-of-war, when ploughing the foaming waves before a fresh breeze, feels that he can scarcely satisfy himself with gazing on the spectacle presented by the circling waves. Wherever the ship’s side rises above the waves, bluish or reddish flames seem to flash lightning-like upwards from the keel. The appearance presented in the tropical seas on a dark night is indescribably glorious, when shoals of dolphins are seen sporting around, and cutting the foaming waves in long and circling lines, gleaming with bright and sparkling light. In the Gulf of Cariaco, between Cumana and the Peninsula of Maniquarez, I have spent hours in enjoying this spectacle.

Le Gentil and the elder Forster ascribed these flames to the electrical friction of the water on the vessel as it glides forward—an explanation that must, in the present condition of our physical knowledge, be regarded as untenable.[^[KD]]

There are probably few subjects of natural investigation which have excited so many and such long-continued contentions as the phosphorescence of sea-water. All that is known with certainty regarding this much disputed question may be reduced to the following simple facts. There are many luminous mollusca which possess the property when alive of emitting at will a faint phosphoric light; which is of a bluish tinge in Nereis noctiluca, Medusa pelagica var. β,[^[KE]] and in the pipe-like Monophora noctiluca, discovered in Baudin’s expedition.[^[KF]] The luminosity of sea-water is in part owing to living light-bearing animals, and in part to the organic fibres and membranes of the same, when in a state of decomposition. The first-named of these causes of the phosphorescence of the ocean is undoubtedly the most common and the most widely diffused. The more actively and the more efficiently that travellers engaged in the study of nature have learnt to employ powerful microscopes, the more our zoological systems have been enriched by new groups of mollusca and infusoria, whose property of emitting light either at will or from external stimulus has been recognised.

The luminosity of the sea, as far as it depends on living organisms, is principally owing, among zoophytes, to the Acalephæ (the families of Medusæ and Cyaneæ), to some Mollusca, and to an innumerable host of Infusoria. Among the small Acalephæ (Sea-nettles), the Mammaria scintillans presents us, as it were, with the glorious image of the starry firmament reflected in the surface of the sea. When full-grown this little creature scarcely equals in size the head of a pin. The existence of siliceous-shelled luminous infusoria was first shown by Michaelis at Kiel. He observed the coruscation of the Peridinium. (a ciliated animalcule,) of the Cuirass-monad (Prorocentrum micans), and of a rotifer, which he named Synchata baltica,[^[KG]] the same that Focke subsequently found in the lagoons of Venice. My distinguished friend and fellow traveller in Siberia, Ehrenberg, succeeded in keeping two luminous Infusoria of the Baltic alive for nearly two months at Berlin. I examined them with him in 1832; and saw them coruscate in a drop of sea-water on the darkened field of the microscope. When these luminous Infusoria (the largest of which was only ⅛ and the smallest from ¹⁄₄₈ to ¹⁄₉₆ of a of a Parisian line in length) were exhausted, and ceased to emit sparks, they would renew their flashing on being stimulated by the addition of acids or by the application of a little alcohol to the sea-water.

By repeatedly filtering fresh sea-water, Ehrenberg succeeded in procuring a fluid in which a large number of these light-emitting animalcules were accumulated.[^[KH]] This acute observer has found in the organs of the Photocharis which give off flashes of light (either voluntarily or when stimulated), a cellular structure of a gelatinous character in the interior, and which manifests some similarity with the electric organ of the Gymnotus and the Torpedo. “When the Photocharis is irritated, in each cirrus a kindling and a gleaming of separate sparks may be observed, which gradually increase and at length illuminate the whole cirrus; until the living flame runs also over the back of this nereid-like animalcule, making it appear under the microscope like a burning thread of sulphur with a greenish-yellow light. In the Oceania (Thaumanthias) hemisphærica, the number and position of the sparks correspond accurately, at the thickened base, with the larger cirri or organs which alternate with them, a circumstance that merits special attention. The manifestation of this wreath of fire is an act of vitality, and the whole development of light an organic vital process, which exhibits itself in Infusorial animals as a momentary spark of light, and is repeated after short intervals of rest.”[^[KI]]

The luminous animals of the ocean appear, from these conjectures, to prove the existence of a magneto-electric light-generating vital process in other classes of animals besides fishes, insects, mollusca, and acalephæ. Is the secretion of the luminous fluid which is effused in some animalcules, and which continues to shine for a long period without further influence of the living organism (as, for instance, in Lampyrides and Elaterides, in the German and Italian glow-worms, and in the South American Cucuyo of the sugar-cane), merely the consequence of the first electric discharge, or is it simply dependent on chemical composition? The luminosity of insects surrounded by air assuredly depends on physiological causes different from those which give rise to a luminous condition in aquatic animals, fishes, Medusæ, and Infusoria. The small Infusoria of the ocean, being surrounded by strata of salt-water which constitutes a powerful conducting medium, must be capable of an enormous electric tension of their flashing organs to enable them to shine so vividly in the water. They strike like the Torpedo, the Gymnotus, and the Electric Silurus of the Nile, through the stratum of water: whilst electric fishes which, in connection with the galvanic circuit, are capable of decomposing water, and of imparting magnetic power to steel needles. (as I showed more than half a century ago,[^[KJ]] and as John Davy has more recently confirmed,[^[KK]]) yield no indications of electricity through the smallest intervening stratum of flame.

The considerations which we have here developed render it probable that one and the same process operates, alike in the smallest living organisms invisible to the naked eye, in the contests of the serpent-like Gymnoti, in the flashing luminous Infusoria which impart such glorious brilliancy to the phosphorescence of the sea, in the thunder-cloud and in the terrestrial or polar light (the silent magnetic flashes), which, caused by an increased tension of the interior of the earth, are announced, for some hours previously, by the sudden variations of the magnetic needle.[^[KL]]

Sometimes one cannot, even with high magnifying powers, discover any animalcules in the luminous water; and yet, wherever a wave breaks in foam against a hard body, and, indeed, wherever water is violently agitated, flashes of light become visible. The cause of this phenomenon depends probably on the decomposing fibres of dead Mollusca, which are diffused in the greatest abundance throughout the water. If this luminous water be filtered through finely woven cloths, the fibres and membranes appear like separate luminous points. When we bathed at Cumana, in the gulf of Cariaco, and walked naked on the solitary beach in the beautiful evening air, parts of our bodies remained luminous from the bright fibres and organic membranes which adhered to the skin, nor did they lose this light for some minutes. If we consider the enormous quantity of Mollusca which animate all tropical seas, we can hardly wonder that sea-water should be luminous, even where no fibres can be visibly separated from it. From the endless subdivision of the masses of dead Dagysæ and Medusæ the whole ocean may, in fact, be regarded as a fluid containing gelatine, and, as such, luminous and of a nauseous taste; unfit for the use of man, but capable of affording nourishment to many species of fish. On rubbing a board with a portion of the Medusa hysocella, the surface thus rubbed recovers its phosphorescence when friction is applied by means of the dry finger. During my voyage to South America I occasionally placed a Medusa on a tin plate, and I then observed that if I struck the plate with another metallic substance the slightest vibrations of the tin were sufficient to cause the animal to emit light. How do the blow and the vibrations here act? Is the temperature momentarily augmented, or are new surfaces presented? or, again, does some gaseous matter such as phosphuretted hydrogen, exude in consequence of this impulse, and burn when it comes in contact with the oxygen of the atmosphere, or with that dissolved in the sea-water, and by which the respiration of the Mollusca is maintained? This light-exciting effect of the blow is most remarkable in a cross or sugar-loaf sea, (mer clapoteuse,) where the waves, clashing from opposite directions, rise in a conical form.

I have seen the ocean, in the tropics, luminous in the most opposite kinds of weather, but most strongly so before a storm, or in a sultry and hazy atmosphere with thick clouds. Heat and cold appear to exercise but little influence on this phenomenon, for, on the Bank of Newfoundland, the phosphorescence is frequently very brilliant in the severest winter. Occasionally, too, the sea will be highly luminous one night, and not at all so on the following, notwithstanding an apparent identity of external conditions. Does the atmosphere favour this development of light? or do all the differences observed during this phenomenon depend on the accidental circumstance of the sea being more or less impregnated, in some parts, with the gelatinous portions of mollusca? Perhaps these phosphorescent social animalcules only rise to the surface under certain conditions of the atmosphere. It has been asked, why our fresh-water swamps which are filled with polyps are not phosphorescent. It would appear that, both in animals and plants, a peculiar mixture of organic particles favours this development of light; thus, for instance, the wood of the willow is more frequently found to be luminous than that of the oak. In England, salt-water has been rendered luminous by mixing herring-brine with it; indeed, it will be easy for any one to convince himself by galvanic experiments, that the luminosity of living animals depends on nervous irritation. I have observed strong phosphorescence emitted from a dying Elater noctilucus, on touching the ganglion of its fore leg with zinc and silver. Medusæ also occasionally emit a stronger light at the moment the galvanic circuit is completed.[^[KM]]

[76]. p. 213—“Which inhabits the lungs of the Rattlesnake of the tropics.”

The animal which I formerly named an Echinorhynchus, and to which I even applied the term Porocephalus, appears, on a closer inspection, according to Rudolphi’s better grounded opinion, to belong to the division of Pentastoma.[^[KN]] It is found in the abdominal cavity and the wide-celled lungs of a species of Crotalus, which, in Cumana, occasionally infests even the interior of houses, and preys on mice. The Ascaris lumbrici[^[KO]] lives beneath the skin of the common earth-worm, and is the smallest of all the species of Ascaris. Leucophra nodulata, Gleichen’s pearl animalcule, has been observed by Otto Friedrich Müller in the interior of the reddish Nais littoralis.[^[KP]] It is probable that these microscopic animals are, in their turn, inhabited by others. All are surrounded by air, deficient in oxygen, and copiously charged with hydrogen and carbonic acid. It is extremely doubtful whether any animal could exist in pure nitrogen, although such an opinion did, formerly indeed, seem warranted with reference to Fischer’s Cistidicola farionis, since, according to Fourcroy’s experiments, the swimming-bladder of fish was presumed to contain air wholly devoid of oxygen. But the experiments made by Erman, and confirmed by myself, prove that the swimming-bladder of fresh-water fish never contains pure nitrogen.[^[KQ]] In sea fish as much as 0·80 parts of oxygen have been found, while, according to Biot’s views, the purity of the air depends on the depth at which the fishes live.[^[KR]]

[77]. p. 214—“The united Lithophytes.”

According to Linnæus and Ellis the calcareous Zoophytes, (among which Madrepores, Meandrinæ, Astrææ, and Pocilloporæ especially produce mural coral-reefs,) are inhabited and invested by animalcules, which were long supposed to be allied to the Nereids belonging to Cuvier’s Annelida (jointed worms). The anatomy of these gelatinous animalcules has been made known by the acute and comprehensive researches of Cavolini, Savigny, and Ehrenberg. We have learned that, in order to understand the whole organism of the (so-called) rock-building animals, we must not consider the scaffolding which remains after their death, namely, the layers of lime formed into delicate lamellæ by a vital function of secretion, as foreign to the soft membranes of the food-receiving animal.

Besides our increased knowledge of the wonderful formation of the living coral-stocks, a more correct view has gradually gained ground respecting the extensive influence which the coral world has exercised on the appearance of low island groups above the level of the sea, on the migration of land-plants, and the successive extension of the domain of the Floras, and, indeed, in some parts of the ocean, on the distribution of the human race and of languages.

As minute social organisms the corals play an important part in the general economy of nature, although they do not, as people began to believe after Capt. Cook’s voyages of discovery, build up islands or enlarge continents from almost unfathomable depths of the ocean. They excite the liveliest interest, whether regarded as physiological objects, and as illustrating the various gradations of animal form, or in connection with the geography of plants, and the geognostic relations of the earth’s crust. According to the comprehensive views of Leopold von Buch, the whole Jura-formation consists of “large elevated coral-banks of the ancient world, surrounding at a certain distance the old mountain chains.”

According to Ehrenberg’s classification,[^[KS]] coral-animals, (in English works often incorrectly termed coral-insects,) are separable into the monostomous Anthozoa, which are either free and with the power of detaching themselves, as Animal-corals; or are attached in the manner of plants, as Phyto-corals. To the first order (Zoocorallia) belong the Hydras or Armpolyps of Trembley, the Actiniæ, radiant with the most splendid colours, and the mushroom-corals; and to the second order belong the Madrepores, the Astrææ, and the Ocellinæ. The Polyps of the second order are those which from their cellular, wave-resisting, wall-works are the principal subject of this illustration. The wall-work is composed of the aggregate of the coral-trunks, which, however, do not suddenly lose their combined vitality, like a dead forest tree.

Every coral-trunk arises by a process of gemmation in accordance with certain laws, and forms one complete structure, each portion being formed by a great number of organically distinct individual animals. In the group of Phyto-corals these cannot separate themselves spontaneously, but remain united with one another by lamellæ of carbonate of lime. Hence each coral-trunk by no means possesses a central point of common vitality.[^[KT]] The propagation of coral-animals, according to the difference of the orders, is by eggs, spontaneous division or gemmation. This last kind of propagation presents the greatest variety of forms in the development of individuals.

The Coral-reefs (or, as Dioscorides designates them, sea-plants, a forest of stony-trees, Lithodendra), are of three kinds; namely, Coast-reefs, (shore-reefs, fringing-reefs), which are directly connected with continental or insular coasts, as on the north-east coast of New Holland, between Sandy Cape and the dreaded Torres Straits, and almost all the coral-banks of the Red Sea examined for eighteen months by Ehrenberg and Hemprich; Island-surrounding reefs (barrier-reefs, encircling-reefs), as at Vanikoro in the small archipelago of Santa Cruz, north of the New Hebrides, and at Puynipete, one of the Carolinas; and Coral-banks surrounding lagoons (Atolls or Lagoon-islands). This very natural division and nomenclature have been introduced by Charles Darwin, and are most intimately connected with the very ingenious explanation which this intellectual naturalist has given of the gradual origin of these wonderful forms. While, on the one hand, Cavolini, Ehrenberg, and Savigny have completed the scientific anatomical knowledge of the organization of coral-animals, on the other, the geographical and geological relations of coral-islands have been investigated, first by Reinhold and George Forster in Cook’s second voyage, and then, after a long interval, by Chamisso, Péron, Quoy and Gaimard, Flinders, Lütke, Beechey, Darwin, d’Urville, and Lottin.

The coral-animals and their stony cellular scaffoldings belong, for the most part, to the warm tropical seas; and the reefs occur most frequently in the Southern Hemisphere. Thus we find the Atolls or Lagoon Islands crowded together in the so-called coral-sea between the north-east coast of New Holland, New Caledonia, Solomon’s Islands, and the Louisiade Archipelago; in the group of the Low Islands (Low Archipelago), eighty in number; in the Fidji, Ellice, and Gilbert Islands; and in the Indian Ocean, north-east of Madagascar, under the name of the Atoll group of Saya de Malha.

The great Chagos Bank, whose structure and dead coral-trunks have been thoroughly investigated by Captains Moresby and Powell, is the more interesting to us, because we may regard it as a prolongation of the more northern Laccadive and Maldive Islands. I have previously directed attention in another work [^[KU]] to the importance of the order of succession of the Atolls, which are exactly in the direction of a meridian as far as 7° south lat., in reference to the general mountain system, and the form of the earth’s surface, in Central Asia. The meridian-chains, which mark the intersection of many mountain-systems running from east to west at the great bend of the Thibetian river Tzang-bo, correspond with the great meridian mountain rampart of the Ghauts and of the more northern Bolor in further or trans-Gangetic India. Here lie the parallel chains of Cochin China, Siam, and Malacca, as well as those of Ava and Arracan, which, after courses of unequal length, all terminate in the gulfs of Siam, Martaban, and Bengal. The bay of Bengal appears like an arrested effort of nature to produce an inland sea. A deep inbreak of the waters, between the simple western system of the Ghauts, and the very complex eastern trans-Gangetic system, has swallowed up a great part of the eastern lowlands, but met with an impediment not so easily overcome in the early existing and extensive table-land of Mysore.

An oceanic inbreak of this nature has given rise to two almost pyramidal peninsulas of very different length and narrowness; and the prolongation of two opposing meridian systems, the mountain system of Malacca in the east, and the Ghauts of Malabar in the west, manifests itself in submarine, symmetrical series of islands, on the one side in the Andaman and Nicobar Islands, which are poor in corals, and on the other in three long-extended archipelagos of Atolls—the Laccadives, the Maldives, and Chagos. The last, called by mariners the Chagos Bank, forms a lagoon, belted by a narrow, and already much broken coral-reef. The length of this lagoon is 88, and its breadth 72 miles. Whilst the enclosed lagoon is only from 17 to 40 fathoms deep, bottom was scarcely found at a depth of 210 fathoms at a small distance from the outer margin of the coral wall, which appears to be now sinking.[^[KV]] At the coral-lagoon, known as Keeling-Atoll, south of Sumatra, Captain Fitz-Roy states, that at only 2000 yards from the reef, no soundings were found with 7200 feet of line.

“The forms of coral, which in the Red Sea rise in thick wall-like masses, are Mæandrinæ, Astrææ, Favia, Madrepores (Porites), Pocillopora (Hemprichii), Millepores, and Heteropores. The latter are among the most massive, although they are branched. The deepest coral trunks, which magnified by the refraction of light, appear to the eye to resemble the dome of a cathedral, belong, as far as could be determined, to Mæandrinæ and Astrææ.”[^[KW]] A distinction must be made between single and in part free polyp-trunks, and those which form wall-like rocks.

If the accumulation of building polyp-trunks in some regions is so striking, it is no less astonishing to observe the perfect absence of these structures in other and often adjacent regions. Their presence or absence must be determined by certain, still uninvestigated, relations of currents, by the partial temperature of the water, and by the abundance or deficiency of nutriment. That certain delicate-branched corals, with less calcareous deposition on the side opposite to the mouth, prefer the stillness of the interior lagoons, is not to be denied; but this preference for still water must not, as has too often happened,[^[KX]] be regarded as a peculiarity of the whole class of these animals. According to the experiences of Ehrenberg and Chamisso in the Red Sea and in the Marshall Islands, which abound in Atolls and lie east of the Caroline Islands, and according to the observations of Captains Bird Allen and Moresby in the West Indies and in the Maldives, we find that living Madrepores, Millepores, Astræas, and Mæandrinas, can support “a tremendous surf;”[^[KY]] and indeed seem to prefer localities the most exposed to the action of storms. The vital forces of the organism regulating the cellular structure, which with age acquires a rocky hardness, resist most triumphantly the mechanical forces,—the shock of moving waters.

In the South Pacific there is a perfect absence of coral-reefs at the Galapagos and along the whole of the west coast of the New Continent, notwithstanding their vicinity to the numerous Atolls of the Low Islands, and the Archipelago of Mendaña or the Marquesas. It is true that the current of the South Pacific, which washes the coasts of Chili and Peru. (and whose low temperature I observed in the year 1802,) is only 60°.1 Fahr., while the undisturbed water at the sides of the cold current is from 81°.5 to 83°.7 Fahr. at Punta Parima, where it deflects to the west. Moreover at the Galapagos there are small currents between the islands, having a temperature of only 58°.3 Fahr. But this lower temperature does not prevail further northwards along the coasts of the Pacific from Guayaquil to Guatimala and Mexico, neither does it prevail in the Cape de Verd Islands, on the whole west coast of Africa, or at the small islands of St. Paul, St. Helena, Ascension, and San Fernando Noronha; yet in none of these are there coral-reefs.

If this absence of reefs characterises the western coasts of America, Africa, and New Holland, they are, on the other hand, of frequent occurrence on the eastern coasts of tropical America, on the African coast of Zanzibar, and on the southern coast of New South Wales. The best opportunities I have enjoyed for personally examining coral banks have been in the Gulf of Mexico, and south of the Island of Cuba, in the so-called “Gardens of the King and Queen” (Jardines y Jardinillos del Rey y de la Reyna). It was Christopher Columbus himself who, on his second voyage, in May, 1494, gave this name to this little group of islands, because from the pleasant association of the silver-leaved arborescent Tournefortia gnapholoides, of flowering species of Dolichos, of Avicennia nitida, and mangrove-thickets (Rhizophora), the coral-islands formed as it were an archipelago of floating gardens. “Son Cayos verdes y graciosos llenos de arboledas,” says the admiral. On my voyage from Batabano to Trinidad de Cuba, I remained for several days in these gardens, which lie to the east of the great Isle of Pines, abounding in mahogany, for the purpose of determining the longitude of the different Cayos.

The Cayos Flamenco, Bonito, de Diego Perez, and de Piedras, are coral islands, rising only from 8 to 15 inches above the level of the sea. The upper edge of the reef does not consist merely of dead polyp-trunks, but is rather formed of a true conglomerate, in which angular pieces of coral, lying in various directions, are embedded in a cement composed of granules of quartz. In Cayo de Piedras I saw such embedded masses of coral, some of them measuring upwards of three cubic feet. Several of the West Indian smaller coral islands have fresh water, a phenomenon which merits a careful investigation wherever it occurs (as for instance near Radak in the South Sea),[^[KZ]] since it has sometimes been ascribed to hydrostatic pressure, acting from a distant coast (as in Venice, and in the Bay of Xagua, east of Batabano), and sometimes to the filtration of rain-water.[^[LA]]

The living gelatinous covering of the calcareous fabric of the coral-trunks attracts fishes and even turtles in search of food. In the time of Columbus the now desolate district of the Jardines del Rey was animated by a singular branch of industry pursued by the inhabitants of the sea-coasts of Cuba, who availed themselves of a little fish, the Remora, or sucking-fish (the so-called Ship-holder), probably the Echeneis naucrates, for catching turtles. A long and strong line, made of the fibres of the palm, was attached to the tail of the fish. The Remora (called in Spanish Reves, or reversed, because at first sight the back and abdomen might easily be mistaken for each other), attaches itself by suction to the turtle through the indented and moveable cartilaginous plates of the upper shell that covers the head. The Remora, says Columbus, would rather let itself be torn to pieces than relinquish its prey, and the little fish and the turtle are thus drawn out of the water together. “Nostrates,” says Martin Anghiera, the learned secretary of Charles V, “piscem Reversum appellant, quod versus venatur. Non aliter ac nos canibus gallicis per æquora campi lepores insectamur, illi (incolæ Cubæ insulæ) venatorio pisce pisces alios capiebant.”[^[LB]] We learn from Dampier and Commerson, that this artifice of employing a sucking-fish to catch other fishes is very common on the eastern coasts of Africa, near Cape Natal and Mozambique, as well as on the island of Madagascar.[^[LC]] An acquaintance with the habits of animals, and the same necessities, lead to similar artifices and modes of capture amongst tribes having no connection with one another.

Although, as we have already remarked, the actual seat of the Lithophytes who build calcareous walls, lies within a zone extending from 22 to 24 degrees on either side of the equator, yet coral-reefs, favoured, it is supposed, by the warm Gulf Stream, are met with around the Bermudas in 32° 23′ lat., and these have been admirably described by Lieutenant Nelson.[^[LD]] In the southern hemisphere corals (Millepores and Cellepores) are found singly as far as Chiloe and even to the Chonos-Archipelago and Tierra del Fuego, in 53° lat., while Retepores have even been found as far as 72½° lat.

Since Captain Cook’s second voyage, the hypothesis advanced by him as well as by Reinhold and George Forster, that the flat coral islands of the South Pacific have been built up by living agents from the depths of the sea’s bottom, has found numerous advocates. The distinguished naturalists Quoy and Gaimard, who accompanied Captain Freycinet on his voyage of circumnavigation in the frigate “Uranie,” were the first who expressed themselves, in 1823, with much freedom against the views advanced by the two Forsters (father and son), by Flinders, and Péron.[^[LE]] “In directing the attention of naturalists to coral-animalcules,” they say, “we hope to be able to prove that all which has been hitherto affirmed or believed up to the present time, regarding the immense structures they are capable of raising, is for the most part inexact, and in all cases very greatly exaggerated. We are rather of opinion that coral-animalcules, instead of rearing perpendicular walls from the depths of the Ocean, only form strata or incrustrations of some few toises in thickness.” Quoy and Gaimard (p. 289) have also expressed an opinion, that Atolls (coral walls inclosing a lagoon) owe their origin to submarine volcanic craters. They have undoubtedly underrated the depth at which animals who construct coral-reefs (as for example the Astræa) can exist, as they place the extreme limits at from 26 to 32 feet below the level of the sea. Charles Darwin, a naturalist, who has known how to enhance the value of his own observations by a comparison with those of others in many parts of the world, places the region of living coral-animals at a depth of 20 or 30 fathoms,[^[LF]] which corresponds with that in which Professor Edward Forbes found the greatest number of corals in the Ægean Sea. This is Professor Forbes’s fourth region of marine-animals, as given in his ingenious memoir on the Provinces of Depth, and the geographical distribution of Mollusca at perpendicular distances from the surface.[^[LG]] It would appear, however, that the depth at which corals live is very different in the different species, especially in the more delicate ones which do not form such considerable structures.

Sir James Ross, in his Antarctic expedition, brought up corals from a great depth with the lead; and these he remitted for accurate examination to Mr. Stokes and Professor Forbes. Westward of Victoria Land, in the neighbourhood of the Coulman Island, in 72° 31′ south lat., and at a depth of 270 fathoms, Retepora cellulosa, a Hornera, and Prymnoa Rossii. (the latter very similar to a species common to the coasts of Norway,) were found alive and in a perfectly fresh condition.[^[LH]] In the far north too, the Greenland Umbellaria Grœnlandica has been brought up alive by whale fishers from a depth of 236 fathoms.[^[LI]] The same relation between species and locality is met with among sponges, which however are now regarded as belonging more to plants than to zoophytes. On the shores of Asia Minor, the common marine sponge is brought up from depths varying from 5 to 36 fathoms, although one very small species of the same genus is only found at a depth of at least 180 fathoms.[^[LJ]] It is difficult to divine what hinders the Astræas, Madrepores, Mæandrinas, and the whole group of tropical phyto-corals, which are capable of constructing large cellular calcareous walls, from living in very deep strata of water. The decrease of temperature is very gradual, the diminution of light nearly the same, and the existence of numerous Infusoria at great depths of the Ocean proves that there cannot here be any deficiency of food for polyps.

In opposition to the hitherto generally adopted opinion respecting the absence of all organisms and living creatures in the Dead Sea, it is worthy of notice that my friend and fellow-labourer, M. Valenciennes, has received, through the Marquis Charles de l’Escalopier, and through the French Consul Botta, beautiful specimens of Porites elongata from the Dead Sea. This fact is the more interesting, because this species is not found in the Mediterranean, but only in the Red Sea, which, according to Valenciennes, has but few organisms in common with the Mediterranean. As a sea-fish, a species of Pleuronectes, advances far into the interior of France, and accustoms itself to gill-respiration in fresh water, so also does a remarkable flexibility of organization exist in the above-mentioned coral-animal (Porites elongata of Lamarck), as the same species lives both in the Dead Sea, which is supersaturated with salt, and in the open ocean near the Séchelles Islands.[^[LK]]

According to the most recent chemical analyses of the younger Silliman, the genus Porites, like many other cellular coral-trunks (Madrepores, Astræas, and Mæandrinas of Ceylon and the Bermudas), contains besides from 92 to 95 per cent. of carbonate of lime and magnesia, a portion of fluorine and phosphoric acid.[^[LL]] The presence of fluorine in the hard skeleton of the polyps reminds us of the fluoride of calcium found in fish bones according to Morechini’s and Gay-Lussac’s experiments at Rome. Silex is mixed only in very small quantities, with the fluoride of calcium and phosphate of lime found in the coral-trunks; but one coral animal allied to the Horn corals (Gray’s Hyalonema, Glass thread) has an axis of fibres of pure silex, resembling a hanging tuft of hair. Professor Forchhammer, who has recently been engaged in a thorough analysis of sea-water in the most opposite parts of the earth’s surface, finds the quantity of lime in the Caribbean Sea remarkably small, it being only ²⁴⁷⁄₁₀₀₀₀, whilst in the Cattegat it amounts to ³⁷¹⁄₁₀₀₀₀. He is disposed to ascribe this difference to the numerous coral-banks near the West India Islands, which appropriate the lime to themselves, and thus exhaust the sea-water.[^[LM]]

Charles Darwin has with great ingenuity developed the genetic connection between shore-reefs, island-encircling reefs, and lagoon islands, i. e., narrow, annular coral banks which surround inner lagoons. According to his views, these three kinds of structure depend upon the oscillating condition of the bottom of the sea, or on periodical elevations and subsidences. The often-advanced hypothesis, according to which the lagoon-islands, or atolls, mark by their circularly enclosed coral-reefs, the outline of a submarine crater, raised on a volcanic crater-margin, is opposed by the great extent of their diameters, which are in some instances upwards of 30, 40, or even 60 miles. Our fire-emitting mountains have no such craters, and if we would compare the lagoon, with its submerged mural surface and narrow encircling reef, with one of the annular lunar mountains, we must not forget that these annular mountains are not volcanoes, but tracts of land enclosed by walls. According to Darwin, the following is the process of formation. An island mountain closely encircled by a coral reef subsides, while the fringing reef that had sunk with it, is constantly recovering its level owing to the tendency of the coral animals to regain the surface by renewed perpendicular structures; these constitute first a reef encircling the island at a distance, and subsequently, when the inclosed island has wholly subsided, an atoll. According to this view, which regards islands as the most prominent parts, or the culminating points of the submarine land, the relative position of the coral islands would disclose to us what we could scarcely hope to discover by the sounding line, viz., the former configuration and articulation of the land. This attractive subject (to the connection of which with the migrations of plants and the distribution of the races of men we drew attention at the beginning of this note), can only be fully elucidated when we shall succeed in acquiring further knowledge of the depth and nature of the different rocks which serve as a foundation for the lower strata of the dead polyp-trunks.

[78]. p. 216—“Of the Samothracian Traditions.”

Diodorus has preserved to us these remarkable traditions, the probability of which has invested them with almost historical certainty in the eyes of geologists. The island of Samothrace, once also named Ethiopea, Dardania, and Leucania or Leucosia in the Scholiast of Apollonius Rhodius, the seat of the ancient mysteries of the Cabiri, was inhabited by the remnant of an aboriginal people, several words of whose vernacular language were preserved in later times in sacrificial ceremonies. The position of Samothrace, opposite to the Thracian Hebrus, and near the Dardanelles, explains why a more circumstantial tradition of the great catastrophe of an outburst of the waters of the Pontus (Euxine) should have been especially preserved in this island. Sacred rites were here performed at altars erected on the supposed limits of this inundation; and among the Samothracians, as well as the Bœetians, a belief in the periodical destruction of the human race (a belief which also prevailed among the Mexicans in their myth of the four destructions of the world) was associated with historical recollections of individual inundations.[^[LN]] According to Diodorus, the Samothracians related that the Black Sea had been an inland lake, which, swelled by the influx of rivers (long prior to the inundations which had occurred among other nations) had burst, first through the straits of the Bosphorus, and subsequently through those of the Hellespont.[^[LO]] These ancient revolutions of nature have been considered in a special treatise, by Dureau de la Malle, and all the facts known regarding them collected by Carl von Hoff, in an important work on the subject.[^[LP]] The Samothracian traditions seem reflected as it were in the Sluice-theory of Strato of Lampsacus, according to which the swelling of the waters in the Euxine first formed the passage of the Dardanelles, and next the opening through the Pillars of Hercules. Strabo, in the first book of his Geography, has preserved among the critical extracts from the works of Eratosthenes, a remarkable fragment of the lost work of Strato, which presents views that embrace almost the whole circumference of the Mediterranean.

“Strato of Lampsacus,” says Strabo,[^[LQ]] “enters more fully than the Lydian Xanthus (who has described the impressions of shells far from the sea) into a consideration of the causes of these phenomena. He maintains, that the Euxine had formerly no outlet at Byzantium, but that the pressure of the swollen mass of waters caused by the influx of rivers had opened a passage, whereupon the water rushed into the Propontis and the Hellespont. The same thing also happened to our sea (the Mediterranean), for here too a passage was opened through the isthmus at the Pillars of Hercules, in consequence of the filling of the sea by currents, which in flowing off left the former swampy banks uncovered and dry. In proof of this, Strato affirms, first, that the outer and inner bottoms of the sea are different; then that there is still a bank running under the sea from Europe to Lybia, which shows that the inner and outer sea were formerly not united; next that the Euxine is extremely shallow, while the Cretan, the Sicilian and the Sardinian seas are, on the contrary, very deep; the cause of this being that the former is filled with mud from the numerous large rivers flowing into it from the north. Hence too the Euxine is the freshest, and the streams flowing from it are directed towards the parts where the bottom is deepest. It would also appear that if these rivers continue to flow into the Euxine, it will some day be completely choked with mud, for even now, its left side is becoming marshy in the direction of Salmydessus (the Thracian Apollonia), at the part called by mariners ‘The Breasts,’ before the mouth of the Ister and the desert of Scythia. Perhaps, therefore, the Lybian Temple of Ammon may also have once stood on the sea-shore, its present position in the interior of the country being in consequence of such off-flowings of rivers. Strato also conjectures that the fame and celebrity of the Oracle (of Ammon) is more easily accounted for, on the supposition that the temple was on the sea-shore, since its great distance from the coast would otherwise make its present distinction and fame inexplicable. Egypt also was in ancient times overflowed by the sea as far as the marshes of Pelusium, Mount Casius, and Lake Serbonis; for whenever in digging it happened that salt-water was met with, the borings passed through strata of sea-sand and shells, as if the country had been inundated, and the whole district around Mount Casius and Gerrha had been a marshy sea, continuous with the Gulf of the Red Sea. When the sea (the Mediterranean) retreated, the country was uncovered, leaving, however, the present Lake Serbonis. Subsequently the waters of this lake also flowed off, converting its bed into a swamp. In like manner the banks of Lake Mœris resemble more the shores of a sea than those of a river.” An erroneous reading introduced as an emendation by Grosskurd, in consequence of a passage in Strabo,[^[LR]] gives in place of Mœris, “the Lake Halmyris,” but the latter was situated near the southern mouth of the Danube.

The Sluice-theory of Strato led Eratosthenes of Cyrene (the most celebrated in the series of the librarians of Alexandria) to investigate the problem of the uniformity of level in all external seas flowing round continents, although with less success than Archimedes in his treatise on floating bodies.[^[LS]] The articulation of the northern coasts of the Mediterranean as well as the form of its peninsulas and islands had given origin to the geognostic myth of the ancient land of Lyctonia. The origin of the lesser Syrtis, of the Triton Lake,[^[LT]] and of the whole of Western Atlas,[^[LU]] had been embodied in an imaginary scheme of fire-eruptions and earthquakes.[^[LV]] I have recently entered more fully into this question,[^[LW]] in a passage with which I would be allowed to close this note:

“The northern shore of the Mediterranean possesses the advantage of being more richly and variously articulated than the southern or Lybian shore, and this was, according to Strabo, already noticed by Eratosthenes. Here we find three peninsulas, the Iberian, the Italian, and the Hellenic, which, owing to their various and deeply indented contour, form, together with the neighbouring islands and the opposite coasts, many straits and isthmuses. Such a configuration of continents and of islands that have been partly severed and partly upheaved by volcanic agency in rows, as if over far-extending fissures, early led to geognostic views regarding eruptions, terrestrial revolutions, and outpourings of the swollen higher seas into those below them. The Euxine, the Dardanelles, the Straits of Gades, and the Mediterranean with its numerous islands, were well fitted to originate such a system of sluices. The Orphic Argonaut, who probably lived in the Christian era, has interwoven old mythical narrations in his composition. He sings of the division of the ancient Lyctonia into separate islands, ‘when the dark-haired Poseidon in anger with Father Kronion struck Lyctonia with the golden trident.’ Similar fancies, which may often certainly have sprung from an imperfect knowledge of geographical relations, were frequently elaborated in the erudite Alexandrian school, which was so devoted to everything connected with antiquity. Whether the myth of the breaking up of Atlantis be a vague and western reflection of that of Lyctonia, as I have elsewhere shown to be probable, or whether, according to Otfried Müller, ‘the destruction of Lyctonia (Leuconia) refers to the Samothracian tradition of a great flood, which changed the form of that district,’ is a question which it is here unnecessary to decide.”

[79]. p. 217—“Precipitation from the clouds.”

The vertical ascent of currents of air is one of the principal causes of the most important meteorological phenomena. Where a desert or a sandy surface devoid of vegetation is surrounded by a high mountain-chain, the sea-wind may be observed driving a dense cloud over the desert, without any precipitation of vapour taking place before it reaches the crest of the mountains. This phenomenon was formerly very unsatisfactorily referred to an attraction supposed to be exercised by the mountain-chain on the clouds. The true cause appears to lie in the ascent from the sandy plain of a column of warm air, which prevents the condensation of the vesicles of vapour. The more barren the surface, and the greater the degree of heat acquired by the sand, the higher will be the ascent of the clouds, and the less readily will the vapour be precipitated. Over the declivities of mountains these causes cease. The play of the vertical column of air is there weaker; the clouds sink, and their disintegration is effected by a cooler stratum of air. Thus deficiency of rain and absence of vegetation in the desert stand in a reciprocal action to one another. It does not rain because the barren and bare surface of sand becomes more strongly heated and radiates more heat; and the desert is not converted into a steppe or grassy plain because without water no organic development is possible.

[80]. p. 218—“The indurating and heat-emitting mass of the earth.”

If according to the hypothesis of the Neptunists (now long since obsolete), the so-called primitive rocks were also precipitated from a fluid, the transition of the earth’s crust from a condition of fluidity to one of solidity, must have been followed by the liberation of an enormous quantity of caloric, which would have given rise to new evaporation and new precipitations. The more recent these precipitations, the more rapid, the more tumultuous, and the more uncrystalline would they have been. Such a sudden liberation of caloric from the indurating crust of the earth, independent of the latitude, and the position of the earth’s axis, might indeed occasion local elevations of temperature in the atmosphere, which would influence the distribution of plants. The same cause might also occasion a kind of porosity which seems to be indicated by many enigmatical geological phenomena in floetz rocks. I have developed my conjectures on this subject in detail in a small memoir on primitive porosity.[^[LX]] According to the views I have more recently adopted, it appears to me that the variously shattered and fissured earth, with its fused interior, may long have continued in the primeval period, to impart to its oxidised surface a high degree of temperature, independent of its position with respect to the sun and to latitude. What an influence would not, for instance, be exercised for ages to come on the climate of Germany by an open fissure a thousand fathoms in depth, extending from the Adriatic Gulf to the northern coast? Although in the present condition of the earth, long-continued radiation has almost entirely restored the stable equilibrium of temperature first calculated by Fourier in his Théorie analytique de la Chaleur, and the outer atmosphere is now only brought into direct communication with the molten interior of the earth, by means of the insignificant openings of a few volcanoes; yet in the primitive condition of our planet, this interior emitted hot streams of air into the atmosphere through the various clefts and fissures formed by the frequently recurring foldings (or corrugations) of the mountain strata. This emission was wholly independent of latitude. Every newly formed planet must thus in its earliest condition have regulated its own temperature, which was, however, subsequently changed and determined by its position in relation to the central body, the sun. The moon’s surface also exhibits traces of this reaction of the interior upon the crust.

[81]. p. 218—“The mountain-declivities of the most southern parts of Mexico.”

The spherical greenstone in the mountain district of Guanaxuato is perfectly similar to that of the Fichtelberg in Franconia. Both form grotesque domes, which break through and are superimposed on transition argillaceous schists. In the same manner pearl-stone, porphyritic schist, trachyte, and pitch-stone porphyry present analogous forms in the Mexican mountains, near Cinapecuaro and Moran, in Hungary, Bohemia, and in Northern Asia.

[82]. p. 220—“The Colossal Dragon-tree of Orotava.”

This colossal dragon-tree (Dracæna draco) stands in the garden of M. Franqui, in the little town of Orotava, called formerly Taoro, one of the most charming spots in the world. In June, 1799, when we ascended the Peak of Teneriffe, we found that this enormous tree measured 48 feet in circumference. Our measurement was made at several feet above the root. Nearer to the ground Le Dru found it nearly 79 feet. Sir G. Staunton asserts that at an elevation of ten feet from the ground, its diameter is still 12 feet. The height of the tree is not much more than 69 feet. According to tradition it would appear that this tree was venerated by the Guanches (as was the ash-tree of Ephesus by the Greeks, the Plantain of Lydia, which Xerxes decorated with ornaments, also the sacred Banyan-tree of Ceylon), and that in the year 1402, which was the period of Béthencourt’s first expedition, it was as large and as hollow as in the present day. When it is remembered that the dragon-tree is everywhere of very slow growth, we may conclude that the one at Orotava is of extreme antiquity. Berthollet says, in his description of Teneriffe, “On comparing the young dragon-trees which grows near this colossal tree, the calculations we are led to make on the age of the latter strike the mind with astonishment.”[^[LY]] The Dragon-tree has been cultivated from the most ancient times in the Canary isles, in Madeira, and Porto Santo, and that accurate observer, Leopold von Buch, found it growing wild near Iguesti in Teneriffe. Its original habitat is not therefore the East Indies, as has long been believed; and its appearance does not afford any refutation of the opinion of those who regard the Guanches as a wholly isolated primitive Atlantic race, having no intercourse with African or Asiatic nations: The form of the Dracænæ is repeated on the southern extremity of Africa, in the Isle of Bourbon, in China, and in New Zealand. In these remotely distant regions we recognise species of the same genus, but none are to be found in the New Continent, where this form is supplied by the Yucca. The Dracæna borealis of Aiton is a true Convallaria, the nature of both being perfectly identical.[^[LZ]]

I have given a representation, in the last plate of the Picturesque Atlas of my American journey,[^[MA]] of the dragon-tree of Orotava, taken from a drawing made in 1776 by F. d’Ozonne, and which I found among the posthumous papers of the celebrated Borda, in the still unprinted journal entrusted to me by the Dépôt de la Marine, and from which I have borrowed important astronomically-determined geographical, data besides many barometrical and trigonometrical notices.[^[MB]] The measurement of the dragon-tree in the Villa Franqui was made in Borda’s first voyage with Pingré in 1771, and not in the second, made 1776 with Varela. It is asserted, that in the fifteenth century, during the early periods of the Norman and Spanish conquests, mass was performed at a small altar erected in the hollow trunk of this tree. Unfortunately, the Dracæna of Orotava lost one side of its leafy top in the storm of the 21st of July, 1819. There is a fine large English copper-plate engraving, which gives an exceedingly true representation of the present condition of the tree.

The monumental character of these colossal living forms, and the impression of reverence which they have created among all nations, have led, in modern times, to a more careful study of the numerical determination of their age, and of the size of their trunks. The results of such investigations induced the elder Decandolle, (the author of the important treatise, entitled De la Longévité des Arbres,) Endlicher, Unger, and other distinguished botanists to conjecture, that the age of many existing vegetable forms may extend to the earliest historical times, if not to the records of the Nile, at least to those of Greece and Italy. In the Bibliothèque Universelle de Genève (t. xlvii. 1831, p. 50) we find the following passage: “Numerous examples seem to confirm the idea, that there still exist, on our planet, trees of a prodigious antiquity—the witnesses, perhaps, of one or more of its latest physical revolutions. If we consider a tree as the combination of as many individual forms as there have been buds developed on its surface, one cannot be surprised if the aggregate resulting from the continual addition of new buds to the older ones, should not necessarily have any fixed termination to its existence.” In the same manner, Agardh says: “If in each solar year new parts be formed in the plant, and the older hardened ones be replaced by new parts capable of conducting sap, we have a type of growth limited by external causes alone.” He ascribes the short duration of the life of herbaceous plants, “to the preponderance of the production of blossoms and fruit over the formation of leaves.” Unfruitfulness in a plant insures a prolongation of its life. Endlicher adduces the instance of an individual plant of Medicago sativa, var. β versicolor, which lived eighty years because it bore no fruit.[^[MC]]

To the dragon-trees, which, notwithstanding the gigantic development of their closed vascular bundles, must be classed, in respect to their floral parts, in the same natural family as Asparagus and the garden onion, belongs the Adansonia, (the monkey bread-tree, Baobab), undoubtedly among the largest and most ancient inhabitants of our planet. In the earliest voyages of discovery made by Catalans and Portuguese, the sailors were accustomed to carve their names on these two species of trees; not always from a mere wish of perpetuating their memory, but also as “marcos,” or signs of possession, and of the rights which nations assume in virtue of first discovery. The Portuguese mariners often selected for carving on the trees, as a “marco,” or mark of possession, the elegant French motto talent de bien faire, so frequently employed by the Infante Don Henrique, the Discoverer. Thus Manuel de Faria y Sousa says expressly;[^[MD]] “Era uso de los primeros Navegantes de dexar inscrito el motto del Infante, talent de bien faire, en la corteza de los arboles.”[^[ME]] (It was the custom of the early navigators to inscribe the motto of the Infante in the bark of the trees.)

The above-named motto, cut on the bark of two trees by Portuguese navigators in the year 1435, and therefore twenty-eight years before the death of the Infante Don Henrique, Duke of Viseo, is singularly connected, in the history of discoveries, with the discussions that have arisen from a comparison of Vespucci’s fourth voyage with that of Gonzalo Coelho (1503). Vespucci relates, that the Admiral’s ship of Coelho’s squadron was wrecked on an island which was sometimes supposed to be that of San Fernando Noronha; sometimes, Peñedo de San Pedro; and sometimes, the problematical island of St. Matthew. The last-named island was discovered on the 15th of October, 1525, by Garcia Jofre de Loaysa in 2½ south lat., in the meridian of Cape Palmas, and almost in the Gulf of Guinea. He remained there eighteen days at anchor, and found crosses, orange-trees that had become wild, and two trunks of trees having inscriptions that bore the date of ninety years back.[^[MF]] I have in another place,[^[MG]] in an inquiry regarding the trustworthiness of Amerigo Vespucci, more fully considered this problem.

The oldest description of the Baobab (Adansonia digitata) is that of the Venetian, Aloysius Cadamosto. (whose real name was Alvise da Ca da Mosto) in 1454. He found at the mouth of the Senegal. (where he joined Antoniotto Usodimare), trunks, whose circumference he estimated at 17 fathoms, or 112 feet.[^[MH]] He might have compared them to dragon-trees, which he had already seen. Perrottet says,[^[MI]] that he had seen monkey-bread fruit trees, which had a diameter of about thirty-two feet, with a height of only from seventy to eighty-five feet. The same dimensions had been given by Adanson in his voyage, 1748. The largest trunks of the monkey bread-fruit trees, which he himself saw, in 1749, some on one of the small Magdalena islands near Cape de Verd, and others at the mouth of the Senegal, were from 26 to nearly 29 feet in diameter, with a height of little more than 70 feet, and a top measuring upwards of 180 feet across. Adanson, however, makes the remark that other travellers had found trunks having a diameter of about 32 feet.[^[MJ]] French and Dutch sailors had carved their names on the trunks in characters six inches in length. One of these inscriptions was of the fifteenth century,[^[MK]] while all the others were of the sixteenth. From the depth of the cuts, which are covered with new layers of wood,[^[ML]] and from a comparison of the thickness of trunks, whose various ages were known, Adanson computed the age of trees having a diameter of 32 feet at 5150 years.[^[MM]] He however cautiously subjoins the following remarks, in a quaint mode of spelling which I do not alter: “le calcul de l’aje de chake couche n’a pas d’exactitude géometrike.” In the village of Grand Galarques, also in Senegambia, the negroes have adorned the entrance of a hollow Baobab with carvings cut out of wood still green. The inner cavity serves as a place of general meeting in which the community debate on their interests. This hall reminds us of the hollow (specus) in the interior of a plantain in Lycia, in which the Roman ex-consul, Lucinius Mutianus, entertained twenty-one guests. Pliny (xii. 3) gives to a cavity of this kind the somewhat ample breadth of eighty Roman feet. The Baobab was seen by René Caillié in the valley of the Niger near Jenne, by Cailliaud in Nubia, and by Wilhelm Peters along the whole eastern coast of Africa, where this tree, which is called Mulapa, i.e. Nlapa-tree, or more correctly muti-nlapa, advances as far as Lourenzo Marques, almost to 26° south lat. The oldest and thickest trunks seen by Peters “measured from 60 to 75 feet in circumference.” Although Cadamosto observed, in the fifteenth century, eminentia non quadrat magnitudini; and although Golberry [^[MN]] found, in the “Vallée des deux Gagnacks,” trunks only 64 feet in height whose diameter was 36 feet, this disproportion between thickness and height must not be assumed to be general. “Very old trees,” says the learned traveller, Peters, “lose their crowns by gradual decay, while they continue to increase in circumference. On the eastern coast of Africa one not unfrequently meets with trees having a diameter of more than 10 feet which reach the height of nearly 70 feet.”

While therefore the bold calculations of Adanson and Perrottet assign to the Adansonias measured by them, an age of 5150 or even 6000 years, which would make them coeval with the builders of the Pyramids, or even with Menes, and would place them in an epoch when the Southern Cross was still visible in Northern Germany;[^[MO]] the more certain estimations yielded by annular rings, and by the relation found to exist between the thickness of the layer of wood and the duration of growth, give us, on the other hand, shorter periods for our temperate northern zone. Decandolle finds that of all European species of trees, the yew attains the greatest age; and according to his calculations, 30 centuries must be assigned as the age of the Taxus baccata of Braburn in Kent, from 25 to 26 to the Scotch yew of Fortingal, and 14½ and 12 respectively to those of Crowhurst in Surrey and Ripon (Fountains Abbey) in Yorkshire.[^[MP]] Endlicher remarks that “another yew-tree in the churchyard of Grasford, North Wales, which measures more than 50 feet in girth below the branches, is more than 1400 years old, whilst one in Derbyshire is estimated at 2096 years. In Lithuania linden trees have been felled which measured 87 feet round, and in which 815 annular rings have been counted.”[^[MQ]] In the temperate zone of the southern hemisphere some species of the Eucalyptus attain an enormous girth, and as they at the same time attain a height of nearly 250 feet, they afford a singular contrast to our yew trees, which are colossal only in thickness. Mr. Backhouse found in Emu Bay, on the shore of Van Diemen’s Land, Eucalyptus trunks which, with a circumference of 70 feet at the base, measured as much as 50 feet at a little more than 5 feet from the ground.[^[MR]]

It was not Malpighi, as has been generally asserted, but the intellectual Michel Montaigne, who had the merit of first showing, in 1581, in his Voyage en Italie, the relation that exists between the annual rings and the age of the tree.[^[MS]] An intelligent artisan, engaged in the preparation of astronomical instruments, first drew Montaigne’s attention to the significance of the annual rings, asserting that the part of the trunk directed towards the north had narrower rings. Jean Jacques Rousseau entertained the same opinion; and his Emile, when he loses himself in the forest, is made to direct his course in accordance with the deposition of the layers of wood. Recent phyto-anatomical observations [^[MT]] teach us, however, that the acceleration of vegetation as well as the remission of growth, and the varying production of the circles of the ligneous bundles (annual deposits) from the cambium cells, depend on other influences than position with respect to the quarter of the heavens.

Trees which in the case of some examples attain a diameter of more than 20 feet, and an age of many centuries, belong to very different natural families. We may here instance Baobabs, Dragon trees, various species of Eucalyptus, Taxodium distichum. (Rich.,) Pinus Lambertiana. (Douglasii,) Hymenæa Courbaril, Cæsalpinieæ, Bombax, Swietenia Mahagoni, the Banyan tree (Ficus religiosa), Liriodendron tulipifera(?), Platanus orientalis, and our Lindens, Oaks, and Yews. The celebrated Taxodium distichon, the Ahuahuete of the Mexicans (Cupressus disticha, Linn., Schubertia disticha, Mirbel), of Santa Maria del Tule, in the State of Oaxaca, has not a diameter of 60 feet, as stated by Decandolle, but exactly 40½ feet.[^[MU]] The two beautiful Ahuahuetes which I have frequently seen at Chapoltepec (growing in what was probably once a garden or pleasure ground of Montezuma) measure, according to the instructive account in Burkardt’s travels (bd. i. s. 268) only 36 and 38 feet in circumference, and not in diameter, as has often been erroneously maintained. The Buddhists of Ceylon venerate the colossal trunk of the sacred fig-tree of Anurahdepura. The Banyan, which takes root by its branches, often attains a thickness of 30 feet, and forms, as Onesicritus truly expresses himself, a leafy roof resembling a many-pillared tent.[^[MV]] On the Bombax Ceiba see early notices from the time of Columbus in Bembo.[^[MW]]

Among those oak trees which have been very accurately measured, the largest in Europe is undoubtedly the one near Saintes on the road to Cozes, in the Department de la Charente inférieure. This tree, which has an elevation of 64 feet, measures very nearly 30 feet in diameter near the ground, while 5 feet higher up it is nearly 23 feet, and where the main branches begin more than 6 feet. A little room, from 10 feet 8 inches to 12 feet 9 inches in width and 9 feet 7 inches in height, has been cleared in the dead part of the trunk, and a semi-circular bench cut within it from the green wood. A window gives light to the interior, and hence the walls of this little room, which is closed by a door, are gracefully clothed with ferns and lichens. From the size of a small piece of wood that had been cut out over the door, and in which two hundred ligneous rings were counted, the age of the oak of Saintes must be estimated at 1800 or 2000 years.[^[MX]]

With respect to the rose-tree (Rosa canina) reputed to be a thousand years old, which grows in the crypt of the Cathedral of Hildesheim, I learn from accurate information, based on authentic records, for which I am indebted to the kindness of the Stadtgerichts-Assessor Römer, that the main stem only has an age of eight hundred years. A legend connects this rose-tree with a vow of the first founder of the cathedral, Louis the Pious; and a document of the eleventh century says, “that when Bishop Hezilo rebuilt the cathedral, which had been burnt down, he enclosed the roots of the rose-tree within a vault still remaining, raised on the latter the walls of the crypt, which was re-consecrated in 1061, and spread the branches of the rose-tree over its sides.” The stem, still living, is nearly 27 feet in height, and only 2 inches thick, and spreads across a width of 82 feet over the outer wall of the eastern crypt. It is undoubtedly of very considerable antiquity, and well worthy of the renown it has so long enjoyed throughout Germany.

If excessive size, in point of organic development, may in general be regarded as a proof of a long protraction of life, special attention is due, among the thalassophytes of the submarine vegetable world, to a species of fucus, Macrocystis pyrifera, Agardh (Fucus giganteus). This marine plant attains, according to Captain Cook and George Forster, a length of 360 feet, and exceeds therefore the height of the loftiest Coniferous trees, not excepting Sequoia gigantea, Endl. (Taxodium sempervirens, Hook, and Arnott) of California.[^[MY]] Captain Fitz-Roy has confirmed this statement.[^[MZ]] Macrocystis pyrifera grows from 64° south lat. to 45° north lat., as far as the Bay of San Francisco on the north-west coast of the New Continent; indeed Joseph Hooker believes that this species of Fucus advances as far as Kamtschatka. In the waters of the Antarctic seas it is even seen floating between the pack-ice.[^[NA]] The cellular band and thread-like structures of the Macrocystis (which are attached to the bottom of the sea by an adhesive organ resembling a claw) seem to be limited in their length by accidental disturbing causes alone.

[83]. p. 220—“Phanerogamic plants already recorded in herbariums.”

Three questions must be carefully distinguished from one another: 1. How many species of plants have been described in printed works? 2. How many of those discovered—that is to say included in herbariums—still remain undescribed? 3. How many species probably exist on the surface of the earth? Murray’s edition of the Linnæan system contains, including cryptogamic plants, only 10,042 species. Willdenow, in his edition of the Species Plantarum from 1797 to 1807, has described as many as 17,457 species of phanerogamia, reckoning from Monandria to Polygamia diœcia. If to these we add 3000 species of cryptogamic plants, we shall bring the number as given by Willdenow to 20,000. More recent investigations have shown how far this estimate of the species described, and of those preserved in herbariums, falls short of the truth. Robert Brown [^[NB]] first enumerated above 37,000 phanerogamia, and I at that time attempted to describe the distribution of 44,000 species of phanerogamic and cryptogamic plants, over the different portions of the world already explored.[^[NC]] Decandolle finds, on comparing Persoon’s Enchiridium with his Universal System divided into twelve families, that more than 56,000 species of plants may be enumerated from the writings of botanists and European herbariums.[^[ND]] If we consider how many new species have been described by travellers since that time, (my expedition alone afforded 3600 of the 5800 collected species of equinoctial plants), and if we bear in mind that there are assuredly upwards of 25,000 phanerogamic plants, cultivated in all the different botanical gardens, we shall soon see how much Decandolle’s estimate is below the truth. From our complete ignorance of the interior of South America (Mato-Grosso, Paraguay, the eastern declivity of the Andes, Santa-Cruz de la Sierra, and all the countries lying between the Orinoco, the Rio Negro, the Amazon, and Puruz), of Africa, of Madagascar, and Borneo, and of Central and Eastern Asia, the idea involuntarily presents itself to the mind that we are not yet acquainted with one third, or probably even with one fifth part of the plants existing on the earth. Drège has collected 7092 phanerogamic species in Southern Africa alone; and he believes that the flora of that region consists of more than 11,000 phanerogamic species, seeing that in Germany and Switzerland, on an equal area (192,000 square miles,) Koch has described only 3300, and Decandolle only 3645 phanerogamia in France. I would here also instance the new genera, consisting partly of high forest trees, which are still being discovered in the neighbourhood of large commercial towns in the lesser Antilles, although they have been visited by Europeans for the last three hundred years. Such considerations, which I purpose developing more fully at the close of this illustration, seem to verify the ancient myth of the Zend-Avesta, that “the creating primeval force called forth 120,000 vegetable forms from the sacred blood of the bull.”

If therefore no direct scientific solution can be afforded to the question, how many vegetable forms—leafless cryptogamia (water algæ, fungi, and lichens), characeæ, liverworts, foliaceous mosses, marsilaceæ, lycopodiaceæ, and ferns—exist on the dry land, and in the wide basin of the sea, in the present condition of the organic terrestrial life of our planet, it only remains for us to employ an approximative method for ascertaining with some degree of probability certain “extreme limits” (numerical data of minima). Since the year 1815, I have, in my arithmetical considerations on the geography of plants, calculated the numbers expressing the ratio which the aggregate of species of different natural families bears to the whole mass of the phanerogamia in those countries where the latter is sufficiently determined. Robert Brown,[^[NE]] the greatest botanist of our age, had, prior to my researches, already determined the numerical proportion of the principal divisions of vegetable forms, as for instance of acotyledons (Agamæ, cryptogamic or cellular plants) to cotyledons (Phanerogamia, or vascular plants), and of monocotyledons (Endogenæ) to dicotyledons (Exogenæ). He finds the ratio of monocotyledons to dicotyledons in the tropical zone as in the proportion of 1 to 5, and in the frigid zone, in the parallels of 60° north, and 55° south lat. as 1 to 2½.[^[NF]] The absolute numbers of the species are compared together in the three great divisions of the vegetable kingdom, according to the method developed in Brown’s work. I was the first who passed from these principal divisions to the individual families, and considered the number of the species contained in each, in their ratio to the whole mass of phanerogamia belonging to one zone.[^[NG]]

The numerical relations of the forms of plants, and the laws observed in their geographical distribution, admit of being considered from two very different points of view. When we study plants in their arrangement according to natural families, without regard to their geographical distribution, the question arises: What are the fundamental forms or types of organization, in accordance with which the greater number of their species are formed? Are there more Glumaceæ than Compositæ on the earth’s surface? Do these two orders of plants combined, constitute one-fourth of the phanerogamia? What numerical relation do monocotyledons bear to dicotyledons? These are questions of general phytology, a science that investigates the organization of plants and their mutual connection, and therefore has reference to the now existing state of vegetation.

If, on the other hand, the species of plants that have been connected together according to their structural analogy, are considered not abstractedly, but in accordance with their climatic relations, and their distribution over the earth’s surface, these questions acquire a totally different interest. We then examine what families of plants predominate in the torrid zone more than towards the polar circle over other phanerogamia? We inquire, whether the Compositæ are more numerous in the new than in the old world, under equal geographical latitudes or between equal isothermal lines? Whether the forms which gradually lose their predominance in advancing from the equator to the poles, follow a similar law of decrease in ascending mountains situated in the equatorial region? Whether the relations of the different families to the whole mass of the phanerogamia differ under equal isothermal lines in the temperate zones on either side of the equator? These questions belong to the geography of plants properly so called, and are connected with the most important problems that can be presented by meteorology and terrestrial physics. Thus the predominance of certain families of plants determines the character of a landscape, and whether the aspect of the country is desolate or luxuriant, or smiling and majestic. Grasses, forming extended Savannahs, or the abundance of fruit-yielding palms, or social coniferous trees, have respectively exerted a powerful influence on the material condition, manners, and character of nations, and on the more or less rapid development of their prosperity.

In studying the geographical distribution of forms, we may consider the species, genera, and natural families of plants separately. A single species, especially among social plants, frequently covers an extensive tract of land. Thus we have in the north, Pine or Fir forests, and Heaths (ericeta); in Spain, Cistus groves; and in tropical America, collections of one and the same species of Cactus, Croton, Brathys, or Bambusa Guadua. It is interesting to study more closely these relations of individual increase, and of organic development; and here we may inquire, what species produces the greatest number of individuals in one certain zone; or, merely what are the families to which the predominating species belong in different climates. In a very high northern latitude, where the Compositæ and the Ferns stand in the ratios of 1 : 13 and 1 : 25 to the sum of all the phanerogamia (i. e., where these ratios are found by dividing the sum total of all phanerogamia by the number of species included in the family of the Compositæ, or in that of the Ferns); one single species of Fern may, however, cover ten times more space than all the species of the Compositæ taken together. In this case the Ferns predominate over the Compositæ by their mass, and by the number of the individuals belonging to the same species of Pteris, or Polypodium; but they will not be found to predominate, if we only compare the number of the different specific forms of the Filices, and of the Compositæ, with the sum total of all Phanerogamia. As, therefore, multiplication of plants does not follow the same laws in all species, and as all do not produce an equal number of individuals, the quotients obtained by dividing the sum of all phanerogamic plants by the species of one family, do not alone determine the leading features impressed on the landscape, or the physiognomy of nature peculiar to different regions of the earth. If the attention of the travelling botanist be arrested by the frequent repetition of the same species, by its mass, and the uniformity of vegetation thus produced, it will be still more forcibly arrested by the infrequency of many other species useful to man. In tropical regions, where the Rubiaceæ, Myrtles, Leguminosæ, or Terebinthaceæ, compose the forests, one is astonished to meet with so few trees of Cinchona, or of certain species of mahogany (Swietenia), of Hæmatoxylon, Styrax, or balsamic Myroxylon. I would also here refer to the scanty and detached occurrence of the precious febrifuge-bark trees (species of Cinchona) which I had an opportunity of observing on the declivity of the elevated plains of Bogota and Popayan, and in the neighbourhood of Loxa, in descending towards the unhealthy valley of the Catamayo, and to the river Amazon. The febrifuge-bark hunters (Cazadores de Cascarilla), as those Indians and Mestizoes are called at Loxa, who each year collect the most efficacious of all the medicinal barks, the Cinchona Condaminea, among the lonely mountains of Caxanuma, Uritusinga, and Rumisitana, undergo considerable danger in climbing to the summits of the highest forest-trees, in order to obtain an extended view, from which they may distinguish the scattered, slender, and aspiring trunks of the Cinchona, by the reddish tint of their large leaves. The mean temperature of this important forest region (between 4° and 4½° south lat.) varies from 60° to 68° Fahr., at an absolute height of from 6400 to 8000 feet above the level of the sea.[^[NH]]

In considering the distribution of species, we may also, independently of individual multiplication and mass, compare together the absolute number which belong to each family. Such a mode of comparison, which was employed by Decandolle,[^[NI]] has been extended by Kunth to more than 3300 of the species of Compositæ with which we are at present acquainted. It does not show what family preponderates by individual mass, or by the number of its species, over other phanerogamic forms, but it simply indicates how many of the species of one and the same family are indigenous in any one country or portion of the earth. The results of this method are, on the whole, more exact, because they are obtained by a careful study of the separate families, without requiring that the whole number of the phanerogamia of every country should be known. Thus, for instance, the most varied forms of Ferns are found in the tropical zone, each genus presenting the greatest number of species in the temperate, humid, and shaded mountainous parts of islands. While these species are less numerous in passing from tropical regions to the temperate zone, their absolute number diminishes still more in approaching nearer to the poles. Although the frigid zone, as, for instance, Lapland, supports species of the families which are best able to resist the cold, Ferns predominate more over other phanerogamia in Lapland than either in France or Germany, notwithstanding the absolute inferiority of the gross number of ferns indigenous to the northern zone, when compared with other countries. These relations are, in France and Germany, as ¹⁄₇₃ and ¹⁄₇₁, while in Lapland they are as ¹⁄₂₅. These numerical relations (obtained by dividing the sum total of all the phanerogamia of the different floras by the species of each family) were published by me in 1817, in my Prolegomena de distributione geographica Plantarum, and corrected in accordance with the great works of Robert Brown, in my Essay on the Distribution of Plants over the earth’s surface, which I subsequently wrote in French. These relations, as we advance from the equator towards the poles, necessarily vary from the ratios obtained by a comparison of the absolute number of the different species belonging to each family. We often see the value of the fractions increase by the decrease of the denominator, whilst the absolute number of the species is reduced. In the fractional method which I have followed as the most applicable to questions relating to the geography of plants, there are two variable quantities; for in passing from one isothermal line to another, we do not find the sum total of the phanerogamia change in the same proportion as the number of the species of one particular family.

In proceeding from the consideration of these species to that of the divisions established in the natural system according to an ideal series of abstractions, we may direct our attention to genera or races, to families, or even to still higher classes of division. There are some genera, and even whole families, which exclusively belong to certain zones; not merely because they can only thrive under a special combination of climatic relations, but also because they first sprang up within very circumscribed localities, and have been checked in their migrations. The larger number of genera and families have, however, their representatives in all regions of the earth, and at all elevations. The earliest inquiries into the distribution of vegetable forms had reference to genera alone, and are to be found in the valuable work of Treviranus.[^[NJ]] This method is, however, less appropriate for yielding general results, than that which compares the number of the species of each family, or the great leading divisions (acotyledons, monocotyledons, and dicotyledons), with the sum total of the phanerogamia. In the frigid zone, the variety of forms, or the number of the genera, does not decrease in an equal degree with that of the species, there being in these regions relatively more genera and fewer species.[^[NK]] The case is almost the same on the summits of high mountain-chains, where are sheltered individual members of many different genera which one would be disposed to regard as belonging exclusively to the vegetation of the plain.

I have deemed it expedient to indicate the different points of view from which the laws of the distribution of vegetable forms may be considered. It is only when these points of view are confounded together, that we meet with contradictions, which have been unjustly attributed to uncertainty of observation.[^[NL]] When expressions like the following are employed: “This form, or this family diminishes as it approaches towards the cold zone,” or “the true habitat of this form is in such or such a parallel of latitude;” or “this is a southern form,” or, again, “it predominates in the temperate zone;” it should be definitely stated whether reference is made to the absolute number of the species, and the proportion of their predominance according to the increase or decrease of latitude; or whether the meaning conveyed is, that a family, when compared with the whole number of the phanerogamia of a flora, predominates over other families of plants. The impression conveyed to the mind of the predominance of forms, depends literally on the conception of relative quantity.

Terrestrial physics have their numerical elements as well as the cosmical system, and it is only by the united labours of botanical travellers that we can hope gradually to arrive at a knowledge of the laws which determine the geographical and climatic distribution of vegetable forms. I have already observed that in the temperate zone of the northern hemisphere, the Compositæ (Synanthereæ) and the Glumaceæ (in which latter division I place the three families of the Gramineæ, the Cyperoideæ, and the Juncaceæ) constitute the fourth part of all phanerogamia. The following numerical relations are the result of my investigations for seven great families of the vegetable kingdom in one and the same temperate zone:

Glumaceæ	⅛	(Grasses alone ¹⁄₁₂)
Compositæ	⅛
Leguminosæ	¹⁄₁₈
Labiatæ	¹⁄₂₄
Umbelliferæ	¹⁄₄₀
Amentaceæ (Cupuliferæ, Betulineæ, and Salicineæ)	¹⁄₄₅
Cruciferæ	¹⁄₁₉

The forms of organic beings are reciprocally dependent on one another. Such is the unity of nature, that these forms limit each other in obedience to laws which are probably connected with long periods of time. When we have ascertained the number of the species on any particular part of the earth’s surface belonging to one of the great families of the Glumaceæ, the Leguminosæ, or the Compositæ, we may with some degree of probability, form approximative conclusions regarding the number of all the phanerogamia, as well as of the species belonging to the other families of plants growing in the country. The number of the Cyperoideæ determines that of the Compositæ, and the number of the latter determines that of the Leguminosæ; and these estimates, moreover, enable us to ascertain in what classes and orders the Floras of a country are still incomplete, teaching us what harvests may still be reaped in the respective families, if we guard against confounding together very different systems of vegetation.

The comparison of the numerical proportions of families in the different zones which have as yet been well explored, has led me to a knowledge of the laws which determine the numerical increase or decrease of vegetable forms constituting a natural family, in proceeding from the equator to the poles, when compared, for instance, with the whole mass of phanerogamia peculiar to each zone. We must here have regard not only to the direction, but also to the rapidity or measure of the increase. We see the denominator of the fraction, which expresses the ratio, increase or diminish. Thus, for instance, the beautiful family of the Leguminosæ diminishes in proportion as it recedes from the equinoctial zone to the north pole. If we find its ratio for the torrid zone (from 0° to 10° of latitude) ⅒, we shall have for the part of the temperate zone (lying between 45° and 52°) ¹⁄₁₈, and for the frigid zone (between 67° and 70° lat.) only ¹⁄₃₅. The direction followed by the great family of the Leguminosæ (viz., increase towards the equator) is also that of the Rubiaceæ, the Euphorbiaceæ, and especially the Malvaceæ. On the other hand, the Gramineæ and the Juncaceæ (the latter more than the former), the Ericeæ, and Amentaceæ, diminish towards the torrid zone. The Compositæ, Labiatæ, Umbelliferæ, and Cruciferæ, diminish from the temperate zone towards the pole and the equator, and the two latter families most rapidly in the direction of the equatorial region; whilst in the temperate zone the Cruciferæ are three times more abundant in Europe than in the United States of North America. In Greenland the Labiatæ are reduced to only one species, and the Umbelliferæ to two, while the whole number of the phanerogamia still amounts, according to Hornemann, to 315 species.

It must at the same time be observed that the development of plants of different families, and the distribution of their forms, do not depend alone on the geographical, or even on the isothermal latitude; the quotients not being always equal on one and the same isothermal line in the temperate zone, as for instance in the plains of America and in those of the Old Continent. Within the tropics there is a very marked difference between America, the East Indies, and the western coast of Africa. The distribution of organic beings over the surface of the earth does not depend solely on the great complication of thermic and climatic relations, but also on geological causes which continue almost wholly unknown to us, since they have been produced by the original condition of the earth, and by catastrophes which have not affected all parts of our planet simultaneously. The large pachydermata are no longer found in the New Continent, while they still exist under analogous climates in Asia and Africa. These differences, instead of deterring us from the investigation of the laws of nature, should rather stimulate us to study them in all their intricate modifications.

The numerical laws of families, the frequently striking agreement between the ratios, where the species constituting these families are for the most part different, lead us into that mysterious obscurity which envelopes everything connected with the fixing of organic types in the different species of animals and plants, and with all that refers to formation and development. I will take as examples two neighbouring countries—France and Germany—which have both been long since explored. In France many species of Gramineæ, Umbelliferæ, Cruciferæ, Compositæ, Leguminosæ, and Labiatæ are wanting, which are some of the commonest in Germany, and yet the ratios of these six large families are almost identical in both countries. Their relations, which I here give, are as follows:

Families.	Germany.	France.
Gramineæ.	¹⁄₁₃	¹⁄₁₃
Umbelliferæ.	¹⁄₂₂	¹⁄₂₁
Cruciferæ.	¹⁄₁₈	¹⁄₁₉
Compositæ.	⅛	⅐
Leguminosæ.	¹⁄₁₈	¹⁄₁₆
Labiatæ.	¹⁄₂₆	¹⁄₂₄

This correspondence in the number of species of one family compared to the whole mass of the phanerogamia of Germany and France would not exist, if the absent German species were not replaced in France by other types of the same families. Those who delight in conjectures respecting the gradual transformation of species, and who regard the different parrots, peculiar to islands situated near each other, as merely transformed species, will ascribe the remarkable uniformity presented by the above numerical ratios to a migration of the same species, which having been altered by climatic influences, continuing for thousands of years, appear to replace each other. But why have our common Heath, (Calluna vulgaris,) and our Oaks not penetrated to the east of the Ural Mountains, and passed from Europe to northern Asia? Why is there no species of the genus Rosa in the southern, and scarcely any Calceolaria in the northern hemisphere? These are points that cannot be explained by peculiarities of temperature. The present distribution of forms (fixed forms of organization) is no more explained by thermal relations alone, than by the hypothesis of migrations of plants radiating from certain central points. Thermal relations are scarcely sufficient to explain the phenomenon why certain species have fixed limits beyond which they cannot pass, either in the plains towards the pole, or in vertical elevation on the declivities of mountains. The cycle of vegetation of each species, however different may be its duration, requires a certain minimum of temperature to enable it to arrive at the full stage of its development.[^[NM]] But all the conditions necessary to the existence of a plant, either within its natural sphere of distribution or cultivation—such as geographical distance from the pole, and elevation of the locality—are rendered still more complicated by the difficulty of determining the beginning of the thermic cycle of vegetation; by the influence which the unequal distribution of the same quantity of heat among days and nights succeeding each other in groups, exerts on the irritability, the progressive development, and the whole vital process; and lastly, by the secondary influence of the hygrometric and electric relations of the atmosphere.

My investigations regarding the numerical laws of the distribution of vegetable forms may, perhaps, at some future time, be applied successfully to the different classes of vertebrate animals. The rich collections of the Muséum d’histoire naturelle in the Jardin des Plantes at Paris, contained in 1820, at a rough estimate, above 56,000 species of phanerogamic and cryptogamic plants in the herbariums, 44,000 insects (probably below the actual number, although they were thus given me by Latreille), 2500 species of fishes, 700 reptiles, 4000 birds, and 500 mammalia. Europe possesses about 80 mammalia, 400 birds, and 30 reptiles; there are, therefore, five times as many birds as mammalia in the northern temperate zone, (as there are in Europe five times as many Compositæ as Amentaceæ and Coniferæ, and five times as many Leguminosæ as Orchideæ and Euphorbiaceæ). In the southern temperate zone the ratio of the Mammalia bears a sufficiently striking accord with that of Birds, being as 1 : 4·3. Birds (and reptiles even to a greater extent), increase more than mammalia in advancing towards the torrid zone. We might be disposed to believe, from Cuvier’s investigations, that this ratio was different in the earlier age of our planet, and that the number of mammalia that perished by convulsions of nature was much greater than that of birds. Latreille has shown the different groups of insects that increase in advancing towards the pole, or towards the equator, and Illiger has indicated the native places of 3800 birds, according to the quarters of the globe;—a far less instructive method than if they had been given according to zones. We may easily comprehend how, on a given area, the individuals of one class of plants or animals may limit each other’s numbers, and how, after the long-continued contests and fluctuations engendered by the requirements of nourishment and mode of life, a condition of equilibrium may have been at length established; but the causes which have determined their typical varieties, and have circumscribed the sphere of the distribution of the forms themselves, no less than the number of individuals of each form, are shrouded in that impenetrable obscurity which still conceals from our view all that relates to the beginning of things and the first appearance of organic life.

If, therefore, as I have already observed at the beginning of this illustration, we attempt to give an approximative estimate of the numerical limit (“le nombre limite” of the French mathematicians), below which we cannot place the sum of all the phanerogamia on the surface of the earth; we shall find that the surest method will be by comparing the known ratios of the families of plants with the number of the species contained in our herbariums, or cultivated in large botanical gardens. As I have just remarked, the herbariums of the Jardin des Plantes at Paris were, in 1820, already estimated at 56,000 species. I will not hazard a conjecture as to the number that may be contained in the herbariums of England, but the great Paris herbarium, which Benjamin Delessert with the noblest disinterestedness has given up to free and general use, was estimated, at the time of his death, to contain 86,000 species, a number almost equal to that which Lindley, even in 1835,[^[NN]] regarded as the probable number of all the species existing “on the whole earth.” Few herbariums are numbered with care, according to a complete, severe, and methodical separation of the different varieties; while, moreover, we often find no inconsiderable number of plants wanting in the large so-called general herbariums, which are contained in some of the smaller ones. Dr. Klotzsch estimates the whole number of Phanerogamic plants in the Great Royal Herbarium at Schöneberg, near Berlin, of which he is curator, at 74,000 species.

Loudon’s useful work (Hortus britannicus) gives a general view of the species which now are or recently have been, cultivated in English gardens. The edition of 1832 enumerates, including indigenous plants, exactly 26,660 Phanerogamia. We must not confound with this large number of plants that either have been, or still are, cultivated in Great Britain, “all the living plants which may simultaneously be found in an individual botanic garden.” In this last respect the Botanic Garden of Berlin has long been regarded as one of the richest in Europe. The fame of its extraordinary riches rested formerly on a mere approximative estimate of its contents, and, as my old friend and fellow-labourer Professor Kunth, has very correctly remarked,[^[NO]] “it was only by the completion of a systematic catalogue, based on the most careful examination of the species, that an actual enumeration could be undertaken. This enumeration gave somewhat more than 14,060 species; and when we deduct from these 375 cultivated ferns, there remain 13,685 Phanerogamia, among which there are 1600 Composite, 1150 Leguminosæ, 428 Labiatæ, 370 Umbelliferæ, 460 Orchideæ, 60 Palms, and 600 Grasses and Cyperaceæ. If we compare with these numbers the number of species given in recent works, as, for instance, Compositæ (according to Decandolle and Walpers), at about 10,000, Leguminosæ 8070, Labiatæ (Bentham) 2190, Umbelliferæ 1620, Grasses 3544, and Cyperaceæ 2000,[^[NP]] we shall perceive that the Botanic Garden at Berlin cultivates only ⅐, ⅛, and ⅑ of the very large families (Compositæ, Leguminosæ, and Grasses), and as many as ⅕ and ¼ of the already described species belonging to the small families (Labiatæ and Umbelliferæ). If we estimate the number of all the different species of Phanerogamia simultaneously cultivated in all the botanical gardens of Europe at 20,000, we shall find, as they appear to constitute about the eighth part of those already described and contained in herbariums, that the whole number of Phanerogamia must amount to nearly 160,000. This estimate need not be regarded as too high, since scarcely the hundredth part of many of the larger families, as, for instance, Guttifereæ, Malpighiaceæ, Melastomeæ, Myrtaceæ, and Rubiaceæ, belong to our gardens.” If we take the number (26,660 species), given in Loudon’s “Hortus Britannicus,” as the basis, we shall find, from the well-grounded series of inferences drawn by Professor Kunth, and which I borrow from his manuscript notice above referred to, that the estimate of 160,000 will increase to 213,000 species; and even this is still very moderate, since Heynhold, in his “Nomenclator botanicus hortensis” (1846), estimates the species of Phanerogamia already cultivated at 35,600. On the whole, therefore,—and the conclusion is, at first sight, sufficiently striking,—the number of species of Phanerogamia at present known by cultivation in gardens, by descriptions, and in herbariums, is almost greater than that of known insects. According to the average estimates of several of the most distinguished entomologists, whose opinion I have been able to obtain, the number of insects at present described, or contained in collections without being described, may be stated as between 150,000 and 170,000 species. The rich collection at Berlin contains fully 90,000, among which there are about 32,000 beetles. Travellers have collected an immense quantity of plants in remote regions, without bringing with them the insects living upon them, or in the neighbourhood. If, however, we limit these numerical estimates to a definite portion of the earth’s surface that has been the best explored in regard to its plants and insects, as, for instance, Europe, we find the ratio between the vital forms of Phanerogamic plants and those of insects changed to such a degree, that while Europe counts scarcely 7000 or 8000 Phanerogamia, more than three times that number of European insects are at present known. According to the interesting contributions of my friend Dohrn in Stettin, more than 8700 insects have already been collected from the rich fauna of the neighbourhood, and yet there are still many MicroLepidoptera wanting; while the number of Phanerogamia found there scarcely exceeds 1000. The Insect-fauna of Great Britain is estimated at 11,600. Such a preponderance of animal forms will appear less surprising when we remember that several of the large classes of insects live only on animal substances, whilst others subsist on agamic plants (Fungi), and even on those which are subterranean. Bombyx Pini, the Pine Spider, the most destructive of all forest-insects, is infested, according to Ratzeburg, by no less than thirty-five parasitical Ichneumonidæ.

These considerations have led us to the proportion borne by the number of species growing in gardens to the gross number of those already described and preserved in herbariums; it now remains for us to consider the proportion of the latter to the conjectural number of species existing on the whole earth, or, in other words, to test their minimum by the relative numbers of the different families—i. e. by variable multipla. A test of this kind gives, however, such low results for the lower amount, as plainly to show that even in the large families, which appear to have been the most strikingly enriched in recent times by the researches of descriptive botanists, our knowledge is still limited to a very small portion of the treasure actually existing. The Repertorium of Walpers which completes Decandolle’s Prodromus of 1825 to 1846, gives 8068 species of the family of the Leguminosæ. We may assume the mean ratio to be ¹⁄₂₁; since it is ⅒ in the tropical zone, ¹⁄₁₈ in the middle temperate zone, and ¹⁄₃₃ in the cold northern zone. The described Leguminosæ would therefore only lead us to assume that there were 169,400 species of Phanerogamia existing on the earth, whereas the Compositæ, as already shewn, testify to the existence of more than 160,000 known Phanerogamia, i. e. such as have been described or are contained in herbariums. This discrepancy is instructive, and will be further elucidated by the following analogous considerations.

The larger number of the Compositæ, of which Linnæus knew only 785 species, and which have now increased to 12,000, appear to belong to the Old Continent. At least Decandolle described only 3590 American, while he estimated the European, Asiatic, and African species at 5093. This abundance of Compositæ in our vegetable systems is however deceptive, and only apparently considerable; for the quotient of this family (which within the tropical zone is ¹⁄₁₅, in the temperate zone ⅐, and in the frigid zone ¹⁄₁₃) shows that more species of Compositæ than of Leguminosæ have hitherto eluded the diligent research of travellers; for even when multiplied by 12 we only obtain the improbably small number of 144,000 for the sum total of the Phanerogamia! The families of the Grasses and of the Cyperaceæ give still lower results, because a proportionally smaller number of species have been described and collected. We need only cast a glance at the map of South America, and remember that the vast extent of country occupied by the grassy plains of Venezuela the Apure and the Meta, as well as to the south of the woody region of the Amazon, in Chaco, in Eastern Tucuman, and in the Pampas of Buenos Ayres and Patagonia, has either been very imperfectly or not at all explored in relation to botany. Northern and Central Asia present an almost equally extensive territory occupied by steppes; but here a larger proportion of dicotyledonous plants is intermixed with the Gramineæ. If we had sufficient grounds for believing that one-half of all the phanerogamic plants existing on the surface of the earth are known, and if we estimate this number at only 160,000 or at 213,000 known species; we must give to the family of grasses, whose general ratio appears to be ¹⁄₁₂, in the former case at least 26,000, and in the latter 35,000 different species, of which in the first case ⅛, and in the second ⅒ are known.

The following considerations oppose the hypothesis that we are already acquainted with half the Phanerogamia on the earth’s surface. Several thousand species of Monocotyledons and Dicotyledons, and among them lofty arborescent forms, have recently been discovered (I would remind the reader of my own expedition) in districts of a very large extent, which had already been explored by distinguished botanists. Yet that portion of the great continents which has never been visited by botanical observers far exceeds the extent of the parts even superficially traversed. The greatest variety of phanerogamic vegetation, i. e. the greatest number of species on an equal area, is to be met with in the tropical or subtropical zones. It is therefore the more important to bear in mind that we are almost wholly unacquainted, north of the equator, in the New Continent, with the floras of Oaxaca, Yucatan, Guatimala, Nicaragua, the Isthmus of Panama, the Choco, Antioquia, and the Province de los Pastos; while south of the equator, we are equally ignorant of the floras of the boundless forest-region between the Ucayale, the Rio de la Madura, and the Toncantin (three mighty tributaries of the Amazon), as well as of those of Paraguay and the Province de las Missiones. In Africa, we know nothing of the vegetation of the whole of the interior, between 15° north and 20° south lat.; and in Asia we are unacquainted with the floras of the south and south-east of Arabia, where the highlands rise to an elevation of 6400 feet; as also with the floras between the Thian-schan, the Kuen-Lün, and the Himalaya; those of Western China; and those of the great portion of the countries beyond the Ganges. Still more unknown to botanists are the interior portions of Borneo and New Guinea, and of some districts of Australia. Further to the south the number of the species decreases in a most remarkable manner, as Joseph Hooker has ably shown, from his own observation, in his Antarctic Flora. The three islands which constitute New Zealand extend from 34½° to 47¼° of latitude, and as they have besides snow-crowned mountains more than 8850 feet in height, they must exhibit considerable differences of climate. The most northern island has been explored with tolerable accuracy from the time of Banks and Solander’s voyage (with Capt. Cook), to the visits of Lesson, the brothers Cunningham, and Colenso; and yet in more than seventy years, the number of Phanerogamia with which we have become acquainted is below 700.[^[NQ]] This paucity of vegetable species corresponds with the paucity of animal forms. Dr. Joseph Hooker has observed that “Iceland, proverbially barren as it is, and upon which no tree, save a few stunted birches, is to be found, possesses five times as many flowering plants as Lord Auckland’s group and Campbell’s Islands together, although these are situated at from 8° to 10° nearer the equator in the southern hemisphere. The antarctic flora is at once characterised by uniformity and great luxuriance of vegetation, which is attributable to the influence exerted by an uninterruptedly cool and humid climate. In Southern Chili, Patagonia, and Tierra del Fuego (from 45° to 56° lat.) this uniformity is strikingly manifested on the mountains and their declivities no less than in the plains. How great is the difference of species when we compare the flora of the south of France, in the same latitude as the Chonos Islands off the coast of Chili, with the Scottish flora of Argyleshire, in the parallel of Cape Horn. In the southern hemisphere the same types of vegetation pass through many degrees of latitude. In the regions near the north pole ten flowering plants have been collected on Walden Island (80½° north lat.), while there is scarcely a solitary grass to be met with in the South Shetland Islands, although situated 63° south latitude.”[^[NR]] These considerations on the distribution of plants prove that the great mass of the still unobserved, uncollected, and undescribed phanerogamia belong to the tropical zone, and to the contiguous regions extending from twelve to fifteen degrees from it.

I have deemed it not unimportant to draw attention to the imperfect state of our knowledge in this slightly cultivated department of numerical botany, and to treat such questions in a more definite manner than has hitherto been possible. In all conjectures regarding relative numbers, we must first examine the practicability of obtaining the lowest limit; as in the question, of which I have treated elsewhere, regarding the ratio of the gold and silver coined to the quantity of the precious metals existing in a wrought state; or as in the question of how many stars, from the tenth to the twelfth magnitude, are scattered over the heavens, and how many of the smallest telescopic stars may be contained in the Milky Way?[^[NS]] It is an established fact, that if it were possible to ascertain completely by observation the number of species of the large phanerogamic families, we should at the same time obtain an approximate knowledge of the sum-total of all the phanerogamia on the surface of the earth (that is, the numbers included in every family). The more therefore we are enabled, by the progressive exploration of unknown districts, gradually to determine the number of species belonging to any one great family, the higher will be the gradual rise of the lowest limit, and the nearer we shall arrive at the solution of a great numerical vital problem, since the forms, in accordance with still unexplained laws of universal organism, reciprocally limit each other. But is the number of the organisms a constant number? Do not new vegetable forms spring from the ground after long intervals of time, whilst others become more and more rare, and finally disappear? Geology confirms the latter part of this question by means of the historical memorials of ancient terrestrial life. “In the primitive world,” to use the expression of the intellectual Link,[^[NT]] “elements remote from each other blend together in wondrous forms, indicating, as it were, a higher degree of development and articulation in a future period of the world.”

[84]. p. 222—“Whether the height of the aërial ocean and its pressure have always been the same.”

The pressure of the atmosphere has a decided influence on the form and life of plants. This life, owing to the fulness and abundance of the leafy organs provided with interstitial openings, is principally directed outwards. Plants mainly live in and through their surfaces, and hence their dependence on the surrounding medium. Animals are more dependant on internal stimuli; they generate and maintain their own temperature, deriving from muscular movements their electric currents, and the chemical vital processes which arise from and re-act upon those currents. A kind of cutaneous respiration constitutes an active vital function of plants, and depends, so far as it is an evaporation, inhalation, and exhalation of fluids, on atmospheric pressure. Hence Alpine plants are more aromatic and hirsute than others, and more amply provided with numerous exhalants.[^[NU]] Zoonomic experiments teach us, as I have shown in another work, that organs are more abundant and more perfectly developed in proportion to the facility with which their functional requirements are fulfilled. The disturbance occasioned in the respiration of their external integuments, by increased barometric pressure, renders it, as I have elsewhere shewn, very difficult for Alpine plants to thrive in the plain.

Whether the aërial ocean surrounding the earth has always exerted the same mean pressure is a question wholly undecided. We do not even know for certain whether the mean barometric height has remained the same during a hundred years at any one given spot. According to the observations of Poleni and Toaldo, this pressure appeared variable. Doubts were long entertained regarding the accuracy of these views, but the more recent investigations of the astronomer Carlini render it almost probable that in Milan the mean barometric pressure is on the decrease. Perhaps the phenomenon is very local, and dependent on periodic variations in descending currents of air.

[85]. p. 223—“Palms.”

It is remarkable, that of this majestic form of plants—the Palms—some of which rise to more than twice the height of the Royal Palace at Berlin, and which the Indian, Amarasinha, has very characteristically called “kings among grasses,”—only fifteen species had been described up to the time of the death of Linnæus. The Peruvian travellers, Ruiz and Pavon, added only eight; whilst Bonpland and myself, traversing a greater extent of country, from 12° south lat. to 21° north lat., described twenty new species, and distinguished as many more which we named, without however being able to procure their blossoms in a perfect state.[^[NV]] At present (forty-four years after my return from Mexico) more than 440 species of palms, from both continents, have already been scientifically described, including the East Indian species arranged by Griffith. The “Enumeratio Plantarum” of my friend Kunth, which appeared in 1841, contains no fewer than 356 species.

The very few palms belonging, like our Coniferæ, Quercineæ, and Betulineæ, to social plants, are the Mauritian Palm (Mauritia flexuosa), and the two species of Chamærops, of which the Chamærops humilis covers whole tracts of land at the estuary of the Ebro and in Valencia, while the other, Chamærops Mocini, which we discovered on the Mexican shore of the Pacific, is entirely without prickles. In the same manner as there are some species of palms, including Cocos and Chamærops, which are peculiar to sea-coasts, so also is there a certain group of Alpine palms belonging to the region of the tropics, which, if I mistake not, was wholly unknown before my South American journey. Almost all these species of the palm family grow in plains and in a mean temperature of 81°.5 and 86° Fahr., seldom advancing higher up the sides of the Andes than to 1900 feet. The beautiful wax palm (Ceroxylon andicola), the Palmetto of Azufral at the Pass of Quindiu, (Oreodoxa frigida), and the reed-like Kunthia montana (Caña de la Vibora) of Pasto, all flourish at elevations varying from 6400 to 9600 feet above the level of the sea, where the thermometer frequently sinks in the night to 42°.8 and 45°.5 Fahr., and the mean temperature is scarcely 57° Fahr. These Alpine palms are interspersed with nut-trees, yew-leaved species of Podocarpus, and oaks, (Quercus granatensis). I have determined, by accurate barometric measurements, the upper and lower limits of the wax palm. We began to observe it first on the eastern declivity of the Cordilleras of Quindiu, at an elevation of 7929 feet, from whence it ascended to the Garita del Paramo, and Los Volcancitos, as high as about 9700 feet. The distinguished botanist, Don José Caldas, who was long our companion in the mountains of New Granada, and who fell a victim to Spanish party hatred, found, many years after my departure from the country, three species of palms in the Paramo de Guanacos, in the immediate vicinity of the limit of perpetual snow, and therefore, probably at an elevation of nearly 14,000 feet.[^[NW]] Even beyond the tropical region (in lat. 28°), Chamærops Martiana [^[NX]] rises on the advanced spurs of the Himalaya range to a height of 5000 feet.

When we consider the extreme geographical and, consequently, also the climatic limits of palms at spots which are but little elevated above the level of the sea, we find that some forms (the Date Palm, Chamærops humilis, Ch. palmetto, and Areca sapida of New Zealand,) advance far within the temperate zone of both hemispheres, to districts where the mean annual temperature scarcely reaches from 57° to 60° Fahr. If we form a progressive scale of cultivated plants in accordance with the different degrees of heat they require, and begin with the maximum, we have Cacao, Indigo, Bananas, Coffee, Cotton, Date Palms, Orange and Lemon trees, Olives, Spanish Chesnuts, and Vines. In Europe, Date Palms, together with Chamærops humilis, grow in the parallels of 43½° and 44°, as, for instance, on the Genoese Rivera del Ponente, near Bordighera, between Monaco and San Stefano, where there is a palm grove, numbering more than 4000 trees; also in Dalmatia, near Spalatro. It is remarkable that the Chamærops humilis is of frequent occurrence in the neighbourhood of Nice and in Sardinia, whilst it is not found in the Island of Corsica, lying between the two. In the New Continent, the Chamærops palmetto, which is sometimes more than 40 feet high, does not advance further north than 34°; a circumstance that may be explained by the inflection of the isothermal lines. In the southern hemisphere, Robert Brown [^[NY]] found that palms, of which there are only very few (six or seven) species, advance as far as 34° in New Holland; while Sir Joseph Banks saw an Areca, in New Zealand, as far as 38°. Africa, which, contrary to the ancient and still extensively diffused opinion, is poor in species of palms, exhibits only one palm (Hyphæne coriacea) which advances south of the equator, only as far as Port Natal, in 30° lat. The continent of South America presents almost the same limits. East of the chain of the Andes, in the Pampas of Buenos Ayres, and in the Cis-Plata province, palms extend, according to Auguste de St.-Hilaire,[^[NZ]] as far as 34° and 35°. The Coco de Chile, (our Jubæa spectabilis?), the only species of palm indigenous in Chili, advances on the western side of the chain of the Andes, according to Claude Gay,[^[OA]] to an equal latitude, viz., to the Rio Maule.

I will here subjoin the aphoristic observations which, in March, 1801, I noted down while on board ship, at the moment we were leaving the palm region surrounding the mouth of the Rio Sinu, west of Darien, and were setting sail for Carthagena de Indias.

“In the space of two years, we have seen as many as 27 different species of palms in South America. How many then must have been observed by Commerson, Thunberg, Banks, Solander, the two Forsters, Adanson, and Sonnerat, on their extensive travels! Yet, at the moment I am writing, our vegetable systems recognise scarcely more than from fourteen to eighteen methodically described species of palms. The difficulties of reaching and procuring the blossoms of palms are, in fact, greater than can well be conceived; and, in our own case, we were made peculiarly sensible of this in consequence of our having directed our attention especially to palms, grasses, cyperaceæ, juncaceæ, cryptogamia, and numerous other subjects hitherto much neglected. Most of the palms flower only once a year, and this period near the equator is generally about the months of January and February. How few travellers are likely to be in the region of palms precisely during this season! The period of blossoming of particular trees is often limited to a few days, and the traveller commonly finds, on his arrival in the region of palms, that the blossoms have passed away, and that the trees present only fructified ovaries and no male flowers. In an area of 32,000 square miles, there are often not more than three or four species of palms to be found. Who can possibly, during the brief period of flowering, simultaneously visit the various palm regions near the Missions on the Rio Caroni, in the Morichales at the mouth of the Orinoco, in the valley of Caura and Erevato, on the banks of the Atabapo and the Rio Negro, and on the declivity of the Duida? There is, moreover, great difficulty when the trees grow in thick woods or on swampy shores (as at the Temi and Tuamini), in reaching the blossoms, which are often suspended from stems formidably armed with huge thorns, and rising to a height of between 60 and 70 feet. They who contemplate distant travels from Europe for the purpose of investigating subjects of natural history, picture to themselves visions of efficient shears and curved knives attached to poles, ready for securing anything that comes in their way; and of boys who, obedient to their mandates, are prepared, with a cord attached to their feet, to climb the loftiest trees! Unfortunately, scarcely any of these visions are ever realised; while the flowers are almost unattainable, owing to the great height at which they grow. In the missionary settlements of the river net-work of Guiana, the stranger finds himself amongst Indians, who, rendered rich and independent by their apathy, their poverty, and their barbarism, cannot be induced either by money or presents to deviate three steps from the regular path, supposing one to exist. This stubborn indifference of the natives provokes the European so much the more, from his being continually a witness of the inconceivable agility with which they will climb any height when prompted by their own inclination, as, for instance, in the pursuit of a parrot, an iguana, or a monkey, which, wounded by their arrows, saves itself from falling by its prehensile tail. In the month of January the stems of the Palma Real, our Oreodoxa Regia, were covered with snow-white blossoms, in all the most frequented thoroughfares of the Havannah, and in the immediate vicinity of the city; but, although we offered, for several days running, a couple of piastres for a single spadix of the hermaphrodite blossoms to every negro boy we met in the streets of Regia and Guanavacoa, it was in vain, for, in the tropics, no free man will ever undertake any labour attended by fatigue unless he is compelled to do so by imperative necessity! The botanists and painters of the Royal Spanish Commission of Natural History under Count Don Jaruco y Mopox (Estevez, Boldo, Guio, Echeveria), confessed to us that, for several years, they had been unable to examine these blossoms, owing to the absolute impossibility of obtaining them.

“After this statement of the difficulties attending their acquisition, the fact of our being only able, in the course of two years, systematically to describe twelve species of palms, although we had discovered twenty species, may be understood; but I confess it would hardly have been credible to me before I left Europe. How interesting a work might be written on palms by a traveller, who could exclusively devote himself to the delineation, in their natural size, of the spathe, spadix, inflorescence and fruits!” (Thus I wrote many years before the Brazilian travels of Martius and Spix, and the appearance of the admirable work on Palms by the former.)

“There is much sameness in the form of the leaves, which are either feathery (pinnata), or fan-like (palmo-digitata); the leaf-stalk (petiolus) is either without thorns or is sharply serrated (serrato-spinosus). The leaf-form of Caryota urens and Martinezia caryotifolia, which we saw on the banks of the Orinoco and the Atabapo, and subsequently in the Andes, at the pass of Quindiu, as high as 3200 feet above the level of the sea, is almost as peculiar among palms as is the leaf-form of the Gingko among trees. The habitus and physiognomy of palms are expressive of a grandeur of character which it is difficult to describe in words. The stem (caudex) is simple, and very rarely divided into branches after the manner of the Dracæna, as in Cucifera thebaica (the Doom Palm), and in Hyphæne coriacea. It is sometimes disproportionately thick, as in Corozo del Sinu, our Alfonsia oleifera; of a reed-like feebleness, as in Piritu, (Kunthia montana), and the Mexican Corypha nana; of a somewhat fork-like and protuberant form towards the lower part, as in Cocos; sometimes smooth and sometimes scaly, as in the Palma de Covijaó de Sombrero, in the Llanos; or, lastly, prickly, as in Corozo de Cumana and Macanilla de Caripe, having the thorns very regularly arranged in concentric rings.

“Characteristic differences also manifest themselves in the roots, which, in some cases, project about a foot or a foot and a half from the ground, raising the stem on a scaffolding, as it were, or coiled round it in a padded-like roll. I have seen viverras and even very small monkeys pass under the scaffolding formed by the roots of the Caryota. Occasionally the stem is swollen only in the middle, being smaller above and below, as in the Palma Real of the island of Cuba. The green of the leaves is either dark and shining, as in Mauritia Cocos, or of a silvery white on the under side, as in the slender fan-palm, Corypha Miraguama, which we saw in the harbour of Trinidad de Cuba. Sometimes the middle of the fan-like leaf is adorned with concentric yellow and blue stripes, in the manner of a peacock’s tail, as in the prickly Mauritia, which Bonpland discovered on the Rio Atabapo.

“The direction of the leaves is a no less important characteristic than their form and colour. The leaflets (foliola) are either ranged in a comb-like manner close to one another, with a stiff parenchyma (as in Cocos Phœnix), to which they owe the beautiful reflections of solar light that play over the surface of the leaves, which shine with a brilliant verdure in Cocos, and with a fainter and ashy-coloured hue in the date-palm; or sometimes the foliage assumes a reed-like appearance, having a thinner and more flexible texture, and being curled near the extremity (as in Jagua, Palma Real del Sinu, Palma Real de Cuba, and Piritu del Orinoco). This direction of the leaves, together with the lofty stem, gives to the palms their character of high majesty. It is a characteristic of the physiognomical beauty of the palm that its leaves are directed aspiringly upwards throughout the whole period of its duration, (and not only in the youth of the tree, as is the case with the Date-Palm, which is the only one introduced into Europe.) The more acute the angle made by the leaves with the upper part of the stem (that is, the nearer they approach the perpendicular,) the grander and nobler is the form of the tree. How different is the aspect of the pendent leaves of the Palma de Covija del Orinoco y de los Llanos de Calabozo (Corypha tectorum), from the more horizontal leaves of the Date and Cocoa-nut palms, and the lofty heavenward-pointing branches of the Jagua, the Cucurito, and Pirijao.

“Nature seems to have accumulated all the beauties of form in the Jagua palm, which, intermingled with the Cucurito or Vadgihai, whose stem rises to a height of 80 or even more than 100 feet, crowns the granite rocks at the cataracts of Atures and Maypures, and which we also occasionally saw on the lonely banks of the Cassiquiare. Their smooth and slender stems rise to a height of from 64 to 75 feet, projecting like a colonnade above the dense mass of the surrounding foliage. These aërial summits present a marked and beautiful contrast with the thickly-leaved species of Ceiba, and with the forest of Laurineæ, Calophyllum, and the different species of Amyris which surround them. Their leaves, which seldom exceed seven or eight in number, incline vertically upwards to a height of 16 or 17 feet, and are curled at the extremities in a kind of feathery tuft. The parenchyma of the leaf is of a thin grass-like texture, causing the leaflets to wave with graceful lightness on the gently oscillating leaf-stalk. The floral buds burst forth, in all species of palms, from the stem immediately beneath the leaves; and the mode in which this takers place modifies their physiognomical character. Thus in some, as in Corozo del Sinu, the sheath is perfectly erect, and the fruit rises like a thyrsus, resembling the fruits of the Bromelia. In the greater number, the sheaths, which in some species are smooth, and in others very prickly and rough, incline downwards. In some, again, the male blossoms are of a dazzling white, and it may then be seen shining from a great distance; but in most species of palms they are yellow, closely compressed, and of an almost faded appearance, even when they first burst from the spathe.

“In palms with feathery leaves the leaf-stalks either burst from the dry, rough, ligneous portion of the stem (as in Cocos, Phœnix, Palma Real del Sinu), or there rises in the rough part of the stem a grass-green, smooth, and thinner shaft, like one column above another, from which the leaf-stalk springs, as in Palma Real de la Havana, Oreodoxa regia, which excited the admiration of Columbus. In the fan-palms (foliis palmatis), the leafy crown often rests on a layer of dry leaves, which imparts to the tree a character of melancholy solemnity and grandeur (as in Moriche, Palma de sombrero de la Havana). In some umbrella-palms, the crown consists of a very few scattered leaves, raised on slender stalks (as in Miraguama).

“The form and colour of the fruit also present more variety than is generally supposed to be the case in Europe. Mauritia flexuosa has egg-shaped fruits, whose smooth, brown, and scaly surface gives them the appearance of young pine cones. How great is the difference between the large triangular cocoa-nut, the berry of the date, and the small stone-fruit of the Corozo! But of all the fruits of the palm, none can be compared for beauty with those of the Pirijao (Pihiguao) of San Fernando de Atabapo and of San Balthasar. They are oval, and of a golden colour (one-half being of a purplish red); are mealy, without seed, two or three inches in thickness, and hang in clusters like grapes from the summits of their majestic palm-trunks.” I have already spoken in the earlier part of this work of these beautiful fruits, of which there are seventy or eighty clustered together in one bunch, and which can be prepared in a variety of ways like bananas and potatoes.

The spathe enclosing the blossom bursts suddenly open in some species of palms, with an audible report. Richard Schomburgk has like myself observed this phenomenon [^[OB]] in the flowering of the Oreodoxa oleracea. This first opening of the blossoms of the palm accompanied with noise, reminds us of Pindar’s Dithyrambus on Spring, and of the moment when in the Argive Nemæa, “the first opening shoot of the date-palm announces the coming of balmy spring.”[^[OC]]

Palms, bananas, and arborescent ferns constitute three forms of especial beauty peculiar to every portion of the tropical zone; wherever heat and moisture co-operate, vegetation is most exuberant and vegetable forms present the greatest diversity. Hence South America is the most beautiful portion of the palm world. In Asia the palm form is rare, in consequence perhaps of a considerable part of the Indian continent beneath the equator having been destroyed and covered by the ocean in some earlier revolution of our planet. We know scarcely anything of the African palms between the Bay of Benin and the coast of Ajan; and we are, generally speaking, as already observed, acquainted with only a very small number of African palm-forms.

Palms, next to Coniferæ, and some species of Eucalyptus belonging to the family of the Myrtaceæ, afford examples of the loftiest growth. Stems of the Cabbage-palm (Areca oleracea) have been seen from 160 to 170 feet in height.[^[OD]] The Wax-palm, our Ceroxylon andicola, which we discovered in the Montaña de Quindiu on the side of the Andes, between Ibague and Carthago, attains the enormous height of 180 to 190 feet. I was able to make an accurate measurement of the trunks of some of these trees, which had been felled in the woods. Next to the Wax-palm, the Oreodoxa Sancona, which we found in flower in the valley of Cauca, and which affords a very hard and admirable wood for building, appeared to me to be the highest of all American palms. The fact, that notwithstanding the enormous mass of fruit yielded by some single palms, the number of individuals of each species growing wild is not very considerable, can only be explained by the frequent abortive development of the fruit, and by the voracity of the enemies by whom they are assailed from all classes of animals. In the basin of the Orinoco, however, whole tribes find the means of subsistence for many months together in the fruit of the palm. “In palmetis, Pihiguao consitis, singuli trunci quotannis fere 400 fructus ferunt pomiformes, tritumque est verbum inter Fratres S. Francisci, ad ripas Orinoci et Guainiæ degentes, mire pinguescere Indorum corpora, quoties uberem Palmæ fructum fundant.”[^[OE]]

[86]. p. 224—“From the earliest infancy of human civilization.”

We find, as far as history and tradition extend, that the Banana has constantly been cultivated in all continents within the tropical zone. The fact of African slaves having, in the course of centuries, brought some varieties of the Banana fruit to America is as certain as that of the cultivation of this vegetable product by the natives of America prior to its discovery by Columbus. The Guaikeri Indians in Cumana assured us that on the coast of Paria, near the Golfo Triste, the Banana will occasionally produce germinating seeds, if the fruit be suffered to ripen on the stem. It is from this cause, that wild Bananas are occasionally found in the recesses of the forests, in consequence of the ripe seeds being scattered abroad by birds. At Bordones also, near Cumana, perfectly formed and matured seeds have been occasionally found in the fruit of the Banana.[^[OF]]

I have already remarked, in another work,[^[OG]] that Onesicritus and other companions of the great Macedonian, make no mention of high arborescent ferns, although they speak of the fan-leaved umbrella palms and of the tender evergreen verdure of the banana-plantations. Among the Sanscrit names given by Amarasinha for the Banana (the Musa of botanists) we find bhanu-phala (sun-fruit), varana-buscha, and moko. Phala signifies fruit generally. Lassen explains Pliny’s words (xii. 6), “Arbori nomen palæ, pomo arienæ,” to this effect, that “The Roman mistook the word pala, fruit, for the name of the tree, whilst varana, changed in the mouth of a Greek to ouarana, was transformed into ariena. The Arabic mauza, our Musa, may have been formed from moko. The Bhanu fruit seems to approach to Banana fruit.”[^[OH]]

[87]. p. 224—“Form of the Malvaceæ.”

Larger forms of the Mallow appear, as soon as we have crossed the Alps; Lavatera arborea, near Nice and in Dalmatia; and L. olbia, in Liguria. The dimensions of the Baobab (monkey bread-tree) have already been given. (See pp. 270–272.) With the form of the Malvaceæ are associated the botanically allied families of the Byttneriaceæ, (Sterculia, Hermannia, and the blossoms of the large-leaved Theobroma Cacao, whose flowers break forth from the bark of the trunk as well as from the roots); the Bombaceæ (Adansonia, Helicteres, and Cheirostemon); and, lastly, the Tiliaceæ (Sparmannia Africana). Our Cavanillesia plantanifolia of Turbaco, near Carthagena in South America, and the celebrated Ochroma-like Hand-tree, the Macpalxochiquahuitl of the Mexicans, (from Macpalli, the flat of the hand,) Arbol de las manitas of the Spaniards, our Cheirostemon platanoides, are splendid representatives of the mallow form. In the last named, the anthers are connected together in such a manner as to resemble a hand or claw rising from the beautiful purplish-red blossoms. There is in all the Mexican free states only one individual remaining, one single primæval stem of this wonderful genus. It is supposed not to be indigenous, but to have been planted by a king of Toluca, about five hundred years ago. I found that the spot where the Arbol de las Manitas stands is 8825 feet above the level of the sea. Why is there only one tree of the kind? Whence did the kings of Toluca obtain the young tree or the seed? It is equally enigmatical, that Montezuma should not have possessed one of these trees in his botanical gardens of Huaxtepec, Chapoltepec, and Iztapalapan, which were used as late as by Philip the Second’s physician, Hernandez, and of which gardens traces still remain; and it appears no less striking that the Hand-tree should not have found a place among the drawings of subjects connected with natural history, which Nezahual Coyotl, king of Tezcuco, caused to be made, half a century before the arrival of the Spaniards. It is asserted that the Hand-tree grows wild in the forests of Guatimala.[^[OI]] We found two Malvaceæ, Sida Phyllanthos (Cavan.), and Sida Pichinchensis, rising in the equatorial region to the great height of 13,430, and 15,066 feet on the mountain of Antisana and at the volcano of Rucu Pichincha.[^[OJ]] The Saxifraga Boussingaultii rises from 600 to upwards of 700 feet higher, on the declivity of Chimborazo.

[88]. p. 225—“Form of the Mimosæ.”

The delicate and feathery foliage of the Mimosæ, Acaciæ, Schrankiæ, and Desmanthus, may be regarded as peculiarly characteristic of tropical vegetation; although some representatives of this form may also be found without the tropics. In the Old Continent of the northern hemisphere, and indeed in Asia, I can instance only one low shrub, described by Marshal von Bieberstein as Acacia Stephaniana, but which, according to Kunth’s more recent investigations, is a species of the genus Prosopis. This social plant covers the arid plains of the province of Schirvan on the Kur (Cyrus), near New Schamach, as far as the ancient Araxes. Olivier found it also in the neighbourhood of Bagdad. It is the Acacia foliis bipinnatis mentioned by Buxbaum, and which extends towards the north as far as 42° lat.[^[OK]] In Africa the Acacia gummifera (Willd.), extends to Mogador, and therefore as far as 32° north lat.

In the New Continent, Acacia glandulosa (Michaux), and A. brachyloba (Willd.), adorn the banks of the Mississippi and Tennessee, and the Savannahs of the Illinois. The Schrankia uncinata was found by Michaux to penetrate from Florida northwards to Virginia (therefore as far as 37° north lat.). Gleditschia triacanthos is met with, according to Barton, to the east of the Alleghany mountains, as far as 38° north lat., and west of the same range even to 41° north lat. The extreme northern limit of Gleditschia monosperma is two degrees further southward. Such are the boundaries of the Mimosa form in the northern hemisphere, while in the southern hemisphere, beyond the tropic of Capricorn, simple-leaved Acaciæ are found as far as Van Dieman’s Land; the Acacia cavenia described by Claude Gay being even found in Chili between 30° and 37° south lat.[^[OL]] Chili has no true Mimosa, but three species of Acacia; and even in the north of Chili the Acacia cavenia grows only to a height of 12 or 13 feet, whilst in the south, as it approaches the sea-coast, it scarcely rises a foot above the ground. The most sensitive of the Mimosas which we saw in the northern portion of South America, are (next to the Mimosa pudica,) M. dormiens, M. somnians, and M. somniculosa. The irritability of the African sensitive plant was already noticed by Theophrastus (iv. 3), and by Pliny (xiii. 10); but I find the first description of the South American sensitive plants (Dormideras) in Herrera (Decad. ii. lib. iii. cap. 4). The plant first attracted the attention of the Spaniards, in 1518, in the Savannahs on the isthmus round Nombre de Dios (“parece como cosa sensible”), and it was pretended that the leaves (“de echura de una pluma de pajaros,”) only contracted together when they were touched with the finger, and not when brought in contact with a piece of wood. In the small swamps which surround the town of Mompox on the Magdalena River, we discovered a very beautiful aquatic Mimosa (Desmanthus lacustris), a representation of which is given in our “Plantes équinoxiales” (t. i. p. 55, pl. 16). In the chain of the Andes of Caxamarca we found two Alpine Mimosas (Mimosa montana and Acacia revoluta) growing at elevations of from 9000 to nearly 9600 feet above the level of the sea.

As yet no true Mimosa, (in the meaning of the word as established by Willdenow,) nor even any Inga, has been found in the temperate zone. Amongst all the Acacias the Oriental Acacia Julibrissin, which Forskäl has confounded with Mimosa arborea, endures the greatest degree of cold. In the Botanical Garden of Padua there is a high stem of considerable thickness growing in the open air, although the mean temperature of Padua is below 56° Fahrenheit.

[89]. p. 225.—“Heaths.”

We do not, in these physiognomical considerations, by any means comprehend, under the name of Heaths, the whole natural family of the Ericaceæ, which, on account of the similarity and analogy in the flowering parts of the plant, include Rhododendrum, Befaria, Gaultheria, and Escallonia; we limit ourselves to the very accordant and characteristic form of the species of Erica, including Calluna (Erica vulgaris, L.).

“Whilst in Europe Erica carnea, E. tetralix, E. cinerea, and Calluna vulgaris, cover large tracts of country, extending from the plains of Germany, and from France and England, to the extremity of Norway; Southern Africa presents the most varied assortment of species. One single species, Erica umbellata, which is indigenous in the southern hemisphere, at the Cape of Good Hope, is again found in Northern Africa, Spain, and Portugal. Erica vagans and E. arborea also belong to the opposite coasts of the Mediterranean. The former is met with in Northern Africa, in the neighbourhood of Marseilles, in Sicily and Dalmatia, and even in England; the second in Spain, Istria, Italy, and the Canaries.”[^[OM]] The common heath, Calluna vulgaris (Salisbury), which is a social plant, covers large tracts from the mouth of the Scheldt to the western declivity of the Ural. Beyond the Ural both Oaks and Heaths disappear. Both are wanting in the whole of Northern Asia, and in all Siberia, as far as the Pacific. Gmelin [^[ON]] and Pallas [^[OO]] have expressed their astonishment at this disappearance of Calluna vulgaris; which, on the eastern declivity of the Ural chain is even more decided and more sudden than one might be led to conclude, from the words of the last-named great naturalist. Pallas merely says, “ultra Uralense jugum sensim deficit, vix in Isetensibus campis rarissime apparet, et ulteriori Sibiriæ plane deest.” Chamisso, Adolph Erman, and Heinrich Kittlitz collected Andromedas but no Calluna in Kamtschatka and on the north-west coast of America. The accurate knowledge which we at present possess of the mean temperature of different portions of Northern Asia, as well as of the distribution of annual heat throughout the different seasons, in no way explains the non-advance of the Heath to the east of the Ural. Dr. Joseph Hooker has treated with much ingenuity, in a note to his “Flora Antarctica,” of the two contrasting phenomena of the distribution of plants, “uniformity of surface accompanied by a similarity of vegetation”, and again, “instances of a sudden change in the vegetation, unaccompanied with any diversity of geological and other feature.”[^[OP]] Is there an Erica in Central Asia? That which Saunders, in Turner’s “Travels to Thibet,”[^[OQ]] has described in the highlands of Nepaul, besides other European plants (Vaccinium Myrtillus, and V. oxycoccus), as Erica vulgaris, is, according to the opinion communicated to me by Robert Brown, probably the Andromeda fastigiata of Wallich. The absence of Calluna vulgaris and of all species of Erica, throughout the whole of the continental part of America is an equally striking fact, since Calluna is met with in the Azores and in Iceland. It has not hitherto been found in Greenland, but it was discovered some years ago in Newfoundland. The natural family of the Ericaceæ is also almost entirely wanting in Australia, where its place is supplied by the Epacrideæ. Linnæus described only 102 species of the genus Erica, but, according to Klotzsch’s observations, this genus comprises 440 true species, after the varieties have been carefully excluded.

[90]. p. 226—“The Cactus form.”

When the natural family of the Opuntiaceæ is separated from the Grossulariaceæ (species Ribes), and is confined within the limits indicated by Kunth,[^[OR]] we may regard the whole as exclusively American. I am not ignorant, that Roxburgh, in the Flora indica (inedita), mentions two species of Cactus which he regards as peculiar to the south-east of Asia, viz., Cactus indicus, and C. chinensis. Both are widely diffused, originally wild or having become so, and different from Cactus opuntia and C. Coccinellifer; but it is remarkable that this Indian plant should have no ancient Sanscrit name. The so-called Chinese Cactus has been introduced by cultivation into the island of St. Helena. Modern investigations, prosecuted at a period when a more general interest has been awakened in relation to the original distribution of plants, will unquestionably remove the doubts that have frequently been advanced against the existence of Asiatic Opuntiaceæ. We see, in a similar manner, certain vital forms appear separately in the animal world. How long did the Tapir continue to be regarded as a characteristic form of the New Continent! And yet the American Tapir is, as it were, repeated in that of Malacca (Tapirus indicus, Cuv.).

Although the Cactus form belongs, properly speaking, to the tropical regions, there are some species in the New Continent, that are indigenous to the temperate zone on the Missouri and in Louisiana; as, for instance, Cactus missuriensis and C. vivipara. Back, in his northern expedition, saw with astonishment, the banks of the Rainy Lake in lat. 48° 40′ (long. 92° 53′) entirely covered with C. Opuntia. South of the equator the Cactus does not advance further than Rio Itata (lat. 36°) and Rio Biobio (lat. 37¼°) In the part of the chain of the Andes lying within the tropics, I have found species of Cactus (C. sepium, C. chlorocarpus, C. bonplandii) on elevated plains from 9000 to upwards of 10,600 feet above the level of the sea; but in Chili, in the temperate zone, a far more strongly marked Alpine character is exhibited by Opuntia Ovallei, whose upper and lower limits have been accurately determined through barometric measurements by the learned botanist, Claude Gay. The yellow-flowering Opuntia Ovallei, which has a creeping stem, does not descend below 6746 feet, advancing as high as the line of perpetual snow; and even above it, wherever a few masses of rock remain uncovered. These little plants have been gathered at spots lying at an elevation of 13,663 feet above the level of the sea.[^[OS]] Some species of Echinocactus are also true alpine plants in Chili. A counterpart to the much admired fine-haired Cactus senilis is presented by the thick-wooled Cereus lanatus, called by the natives Piscol, which has a fine red fruit. We found it near Guancabamba, in Peru, on our journey to the Amazon river. The dimensions of the Cactaceæ (a group on which the Prince of Salm-Dyck was the first to throw considerable light) present the most striking contrasts. Echinocactus Wislizeni, which has a circumference of seven feet and a half, with a height of four feet and a quarter, is only third in size, being surpassed by E. ingens, (Zucc.) and E. platyceras. (Lem.)[^[OT]] The Echinocactus Stainesii attains a diameter of from two feet to two and a-half; E. visnago, belonging to Mexico, has a diameter of upwards of three feet, with a height of more than four feet, and weighs as much as from 700 to 2000 lbs.; while the Cactus nanus, which we collected near Sondorillo, in the province of Jaen, is so small and so loosely rooted in the sand, that it gets between the toes of dogs. The Melocactuses, which are full of juice even in the driest season, as the Ravenala of Madagascar (wood-leaf in the language of the country from rave, raven, a leaf, and ala, the Javanese halas, a wood), are vegetable springs, which the wild horses and mules open by stamping with their hoofs—a process in which they frequently injure themselves.[^[OU]] Cactus Opuntia has spread during the last quarter of a century in a remarkable manner through Northern Africa, Syria, Greece, and the whole of Southern Europe; penetrating from the coasts of Africa far into the interior, where it associates with the native plants.

After being accustomed to see Cactuses only in our hothouses, we were astonished at the density of the woody fibres in old cactus stems. The Indians are aware that cactus wood is indestructible, and admirably adapted for oars and the thresholds of doors. There is hardly any physiognomical character of exotic vegetation that produces a more singular and ineffaceable impression on the mind of the traveller, than an arid plain densely covered with columnar or candelabra-like stems of cactuses, similar to those near Cumana, New Barcelona, Coro, and in the province of Jaen de Bracamoros.

[91]. p. 226—“Orchideæ.”

The almost animal-like form occasionally observed in blossoms of the Orchideæ is most strongly marked in Anguloa grandiflora, celebrated in South America as the Torito; in the Mosquito (our Restrepia antennifera); in the Flor del Espiritu Santo (likewise an Anguloa, according to Floræ Peruvianæ Prodrom. p. 118, tab. 26); in the ant-like flower of Chiloglottis cornuta;[^[OV]] in the Mexican Bletia speciosa; and in the whole host of our remarkable European species of Ophrys: O. muscifera, O. apifera, O. aranifera, O. arachnites, &c. The taste for these splendidly flowering plants has so much increased, that the number of species cultivated by Messrs. Loddige, which, in 1813, was only 115, was upwards of 1650 in 1843, and in 1848, the number was estimated at no fewer than 2360. What a treasure of sumptuously flowering and unknown Orchideæ may be inclosed in the interior of Africa wherever there is an abundant supply of water! Lindley, in his beautiful work, On the Genera and Species of Orchideous Plants, 1840, counted exactly 1980 species; whilst Klotzsch at the close of the year 1848 counted 3545.

Whilst the temperate and cold zone possess only terrestrial Orchideæ, growing close to the ground, both forms, the terrestrial, as well as the parasitical, growing on the trunks of trees, are indigenous in the beautiful regions of the tropics. To the former class belong the tropical genera Neottia, Cranichis, and most Habenarias. But we have found both these forms as alpine plants on the declivity of the Andes of New Granada and Quito, viz., the parasitical (Epidendreæ) Masdevallia uniflora (at an elevation of 10,231 feet), Cyrtochilum flexuosum (at 10,103 feet), and Dendrobium aggregatum (at 9485 feet); and the terrestrial forms of Altensteinia paleacea, near Lloa Chiquito, at the foot of the volcano of Pichincha. Claude Gay is of opinion that the Orchideæ supposed to have been found growing on trees in the Island of Juan Fernandez and even at Chiloe, were probably only parasitical Pourretiæ, which advance as far south at least as 40°. In New Zealand, the tropical form of Orchideæ, hanging from trees, is still to be seen as far south as 45°. But the Orchideæ of Auckland and Campbell Islands (Chiloglottis, Thelymitra, and Acianthus), grow on level ground in moss. In the animal world there is at least one tropical form that penetrates further south. The Island of Macquarie (lat. 54° 39′) has an indigenous parrot, which lives therefore in a region nearer to the south pole than Danzig is to the north pole.[^[OW]]

[92]. p. 226—“Form of the Casuarinæ.”

Acacias, in which the place of the leaves is supplied by phyllodia, Myrtaceæ (Eucalyptus, Metrosideros, Melaleuca, Leptospermum), and Casuarinæ, constitute the sole characteristics of the vegetable world of Australia (New Holland) and Tasmania (Van Diemen’s Land). Casuarinæ with their leafless, thin, thread-like, articulated branches, and their joints furnished with membranous, toothed spathes, have been compared by travellers,[^[OX]] according to differences of species, either with arborescent Equisetaceæ (Horsetails) or with our Scotch firs. I have been much struck with the singular appearance of leaflessness presented by the small thickets of Colletia and Ephedra in South America, near the coast of Peru. Casuarina quadrivalvis penetrates, according to Labillardière, as far south as 43° in Tasmania. The mournful form of the Casuarina is not unknown in the East Indies and even on the eastern coast of Africa.

[93]. p. 227—“Acicular-leaved trees.”

The family of the Coniferæ (including the genera of Dammara, Ephedra, and Gnetum of Java and New Guinea, which are essentially allied to it, though distinctly separated by the form of the leaf and the whole conformation), plays so important a part in consequence of the number of individuals in each species, and by its geographical diffusion, while it covers in the northern temperate zone, as a social plant, such extensive districts, that we are almost compelled to wonder at the inconsiderable number of the species. We are not acquainted with so many Coniferæ by three-fourths as there are Palms already described, nay, the Coniferæ are numerically less than the Aroideæ. Zuccarini, in his “Contributions to the Morphology of the Coniferæ,”[^[OY]] enumerates 216 species, of which 165 belong to the Northern and 51 to the Southern hemisphere. These proportional numbers must now, in consequence of my researches, be differently expressed, since, with the species of Pinus, Cupressus, Ephedra, and Podocarpus, which Bonpland and I discovered in the tropical part of Peru, Quito, New Granada, and Mexico, the number of the cone-bearing trees flourishing between the tropics amounts to 42. The excellent and latest work of Endlicher [^[OZ]] contains 312 species of Coniferæ now living, and 178 of a primeval mundane period which are now buried in the coal formation, in variegated sandstone, in keuper, and in Jura limestone. The vegetation of the eocene world presents especially to us forms which, by their coëval relationship with several families of the present world, remind us that with it many intervening members have disappeared. The Coniferæ, so frequent in the primeval world, accompany, in particular, the ligneous remains of Palms and Cycadeæ; but in the most recent beds of lignite or brown coal we again find Coniferæ, our Pines and Firs, associated with Cupuliferæ (or Mastworts), Maples and Poplars.[^[PA]]

If the surface of the earth did not rise to great altitudes within the tropics, the strikingly characteristic form of acicular-leaved trees would have remained wholly unknown to the inhabitants of that zone. I took great pains, in common with Bonpland, to trace out, in the Mexican Highlands, the lower and upper boundary line of the Coniferæ and Oaks. The heights, at which both begin to grow (los Pinales y Encinales, Pineta et Querceta), are hailed with joy by those who come from the sea coast, because they announce a climate not yet invaded, as far as experience has hitherto shown, by that mortal disease called the black vomit (vomito prieto, a form of the yellow fever). For the oaks, especially the Quercus Xalapensis (one of the twenty-two Mexican species of oak which we first described), the lower line of vegetation, on the way from Vera Cruz to the capital of Mexico, somewhat below the Venta del Encero, is 3048 feet above the sea. At the western slope of the plateau, between the South Sea and Mexico, the inferior line for oaks is something lower; it begins near a hut named Venta de la Moxonera, between Acapulco and Chilpanzingo, at the absolute height of 2481 feet. I found a similar difference in the lower boundary line of the pine-forest. This boundary, towards the South Sea, in the Alto de los Caxones, north of Quaxinquilapa, is for the Pinus Montezumæ (Lamb.), which we at first had considered to be the Pinus occidentalis (Swartz), at the height of 4092 feet; but towards Vera Cruz, at the Cuesta del Soldado, it rises to 5979 feet. Both these kinds of tree, therefore, the oaks and firs as specified above, descended lower towards the Pacific than towards the Caribbean Gulf. During my ascent of the Cofre di Perote, I found the superior boundary Line of the oaks to be 10,353 feet; that of the Pinus Montezumæ 12,936 feet (about 2000 feet higher than the summit of Mount Ætna) and here, in February, considerable masses of snow had already fallen.

The greater the heights at which the Mexican cone-bearing trees begin to show themselves, the more singular is it, in the island of Cuba (where, at the border of the tropical zone the air, it is true, is cooled down during northerly winds to 46°.6 Fahr.), to see another kind of fir (P. Occidentalis, Swartz), in the plain itself, or on the gentle hills of the Isle of Pines, growing among palms and mahogany trees (Swietenia). Columbus even makes mention of a fir-wood (Pinal) in the journal of his first voyage (Diario del 25 de Nov., 1492), at Caya de Moya, north-east of Cuba. At Haiti, too (St. Domingo), the Pinus occidentalis near Cape Samana descends from the mountains down to the very beach. The stems of these firs, wafted by the gulf-stream to the two Azores, Graciosa and Fayal, were among the principal signs that proclaimed to the great discoverer the existence of unknown lands in the West.[^[PB]] Is it positively ascertained that the Pinus occidentalis is entirely absent from Jamaica, notwithstanding its lofty mountains? We may be permitted to inquire also, what kind of Pinus grows on the eastern coast of Guatimala, since the P. tenuifolia (Benth.) is assuredly found only on the mountains near Chinanta.

On taking a general view of the species of plants which form the upper tree-boundary in the northern hemisphere from the frigid zone to the equator; I find, for Lapland, according to Wahlenberg, in the Sulitelma Mountains (lat. 68°), not acicular-leaved trees but birches (Betula alba), far above the upper limit of the Pinus sylvestris; and for the temperate zone I find in the Alps (lat. 45° 45′) Pinus picea (Du Roi), advanced beyond the birches. In the Pyrenees (lat. 42° 30′), we find Pinus uncinata (Ram.) and P. sylvestris, var. rubra; within the tropics in Mexico (lat. 19°–20°), Pinus Montezumæ extends far beyond Alnus toluccensis, Quercus spicata, and Q. crassipes; and in the snow-crowned mountains of Quito, beneath the equator, Escallonia myrtilloides, Aralia avicennifolia, and Drymis Winteri attain the highest limits. This last species of tree, identical with the Drymis granatensis (Mut.), and the Wintera aromatica of Murray, presents, as Dr. Joseph Hooker has shown,[^[PC]] the most singular instance of the uninterrupted dissemination of the same species of tree from the southernmost part of Tierra del Fuego and Hermit Island, where it was discovered as early as 1577 by Drake’s expedition, up to the northern Highlands of Mexico, over a meridian extent of 86° of latitude or 5160 miles. Where the acicular or needle-leaved trees, as in the Swiss Alps and the Pyrenees, and not the birch as in the extreme north, form the boundary of arborescent vegetation on the loftiest mountains, which they picturesquely encircle, they are immediately followed in their ascent towards the snow-crowned summits, in Europe and Western Asia by the Alpine roses, Rhododendra, and at the Silla de Caracas, and the Peruvian Paramo de Saraguru, by the purplish-red blossoms of the graceful Befariæ. In Lapland the Rhododendron laponicum immediately follows the Coniferous trees; in the Swiss Alps, the Rhododendron ferrugineum and R. hirsutum, and in the Pyrenees the R. ferrugineum alone; and in the Caucasus the R. caucasicum. But R. caucasicum has also been found isolated by De Candolle in the Jura mountains (in the Creux de Vent), 5968 feet lower down, at the inconsiderable height of from 3303 to 3730 feet. If we would trace out the last zone of vegetation near the snow line we must name, according to our personal observation, in tropical Mexico, Cnicus nivalis and Chelone gentianoides; in the cold mountainous tracts of New Granada, the woolly Espeletia grandiflora, E. corymbosa, and E. argentea; in the Andes chain of Quito, Culcitium rufescens, C. ledifolium, and C. nivale;—yellow-blossomed Compositæ, which replace the somewhat more northerly lanose herbs of New Granada, and the Epeletiæ, with which they have so much physiognomical resemblance. This substitution or repetition of similar and almost identical forms in regions that are separated from each other by seas or wide intervening tracts, is a wonderful law of nature. It prevails even in the rarest forms of the floras. In Robert Brown’s family of the Rafflesiæ, separated from the Cytineæ, the two Hydnoræ in Southern Africa (H. Africana and H. Triceps), described by Thunberg and Drege, have, in South America, their counterpart in the H. Americana of Hooker.

Far above the regions of Alpine herbs, of the grasses and the lichens, nay, beyond the boundary of perpetual snow, there occasionally appears a phanerogamic plant, growing sporadically, and as it were isolated, to the astonishment of botanists; and this occurs both within the tropics and in the temperate zone, on fragments of rock which remain free from snow and are probably warmed by open fissures. I have already mentioned the Saxifraga Boussingaulti, which is found at a height of 15,773 feet on the Chimborazo; in the Swiss Alps the Silene acaulis, a clovewort or caryophyllea, has been seen at a height of 11,382 feet. The former vegetates at 640, the latter at 2621 feet above the respective local limits of snow, heights which were determined when both the plants were discovered.

In our European Coniferous woods the Red Pine (or Norway Spruce), and the White (or Silver) Pine show great and remarkable variations as regards their geographical dispersion on the slopes of mountains. Whilst in the Swiss Alps the Red Pine (Pinus picea, Du Roi, foliis compressotetragonis; unfortunately named by Linnæus and by most botanists of our time the Pinus abies!), forms the limit of tree vegetation at the mean height of 5883 feet, and only here and there does the lowly alder (Alnus viridis, Dec., Betula viridis, Vill.), advance higher towards the snow-limit; the White Pine (Pinus abies, Du Roi, Pinus picea, Linn., foliis planis, pectinato-distichis, emarginatis), has its limit, according to Wahlenberg, about 1000 feet lower. The Red Pine does not grow at all in Southern Europe, in Spain, the Apennines, and Greece; and, as Ramond remarks, it is only seen on the slope of the northern Pyrenees at great heights, and is entirely wanting in the Caucasus. The Red Pine extends further to the north in Scandinavia than the White, which latter tree appears in Greece (on the Parnassus, the Taygetus, and the Œta), as a variety with long acicular leaves, foliis apice integris, breviter mucronatis, the Abies Apollinis of the acute observer Link.[^[PD]]

On the Himalaya the acicular-leaved form of trees is distinguished by the mighty thickness and height of the stem as well as by the length of the leaf. The chief ornament of the mountain range is the Cedar Deodwara (Pinus deodara, Roxb.), which word is, in Sanscrit, dêwa-dâru, i.e. timber for the gods, its stem being nearly from 13 to 14 feet in diameter. It ascends in Nepaul to more than 11,700 feet above the level of the sea. More than 2000 years ago the Deodwara cedar near the River Behut, that is, the Hydaspes, furnished the timber for the fleet of Nearchus. In the valley of Dudegaon, north of the copper mines of Dhunpoor in Nepaul, Dr. Hoffmeister, so early lost to science, found in a forest the Pinus longifolia (Royle), or the Tschelu Fir, mixed with the lofty stems of a palm—Chamærops martiana (Wallich).[^[PE]] Such an interspersion of the pineta and palmeta had already, in the new continent, excited the astonishment of the companions of Columbus, as a friend and contemporary of the admiral’s, Petrus Martyr Anghiera, relates.[^[PF]] I myself saw, for the first time, this blending of pines with palms on the road from Acapulco to Chilpanzingo. The Himalaya, like the Mexican highlands, besides its genera of pine and cedar, possesses also forms of the Cypress (Cupressus torulosa, Don.); of the Yew (Taxus Wallichiana, Zuccar.); of the Podocarpus (Podocarpus nereifolia, Brown); and the Juniper (Juniperus squamata, Don., and J. excelsa, Bieberst.; the latter species occurring also at Schipke in Thibet, in Asia Minor, Syria, and the Grecian Islands; on the other hand, Thuja, Taxodium, Larix, and Araucaria, are forms of the New Continent, which are wanting in the Himalaya.

Besides the twenty species of pine with which we are acquainted in Mexico, the United States of North America, in their present extension to the Pacific, present forty-five described species, whilst all Europe can only enumerate fifteen. The same difference between abundance and paucity of forms is shown in the oaks, in favour of the New Continent (a quarter of the world the most connected and most elongated in a meridional direction). It has, however, been very recently demonstrated by the extremely accurate researches of Siebold and Zuccarini to be an erroneous assertion, that many European species of pine, in consequence of their wide distribution throughout Northern Asia, passed over to the Japanese islands, and there mingled with a genuine Mexican species, the Weymouth pine (Pinus strobus, L.), as Thunberg asserts. What Thunberg considered to be European species of pine, are species entirely different. Thunberg’s Red Pine (Pinus abies, Linn.) is P. polita, Sieb., and often planted near Buddhist temples; his northern common fir (Pinus sylvestris) is P. Massoniana, Lamb.; his P. cembra, the German and Siberian stone pine-tree, is P. parviflora, Sieb.; his common larch (P. larix) is the P. leptolepis, Sieb.; his Taxus baccata, the fruit of which the Japanese courtiers eat as a precautionary measure when attending long ceremonies,[^[PG]] forms a special genus and is Cephalotaxus drupacea, Sieb. The Japanese islands, despite the proximity of the Asiatic Continent, have a very different character of vegetation. Thunberg’s Japanese Weymouth pine, which would present an important phenomenon, is moreover a naturalized tree, that differs entirely from the indigenous pines of the New World. It is Pinus korajensis, Sieb., which has migrated from the peninsula of Corea and Kamtschatka to Nipon.

Of the 114 species now known of the genus Pinus, there is not one in the whole southern hemisphere, for the Pinus Merkusii, described by Junghuhn and De Vriese, still belongs to that part of the island of Sumatra which is north of the equator, that is, to the district of the Battas. The P. insularis, Endl., belongs to the Philippines, although at first it was introduced into Loudon’s Arboretum as P. timoriensis. From our present increasing knowledge of the geography of plants, we know that there are excluded also from the southern hemisphere, in addition to the genus Pinus, all the races of Cupressus, Salisburia (Ginkgo), Cunninghamia (Pinus lanceolata, Lamb.), Thuja, one species of which (Th. gigantea, Nutt.) at the Columbia river rises as high as 180 feet, Juniperus, and Taxodium (Mirbel’s Schubertia). I can introduce this last genus here with the greater certainty, inasmuch as a Cape plant, Sprengel’s Schubertia capensis, is no Taxodium, but forms a special genus, Widringtonia, Endl., in quite another division of the Coniferæ.

This absence from the southern hemisphere of the true Abietineæ, of the Juniperineæ, Cupressineæ, and all the Taxodineæ, as likewise of the Torreya, of the Salisburia adiantifolia, and of the Cephalotaxus among the Taxineæ, vividly reminds us of the enigmatical and still obscure conditions which determined the original distribution of vegetable forms. This distribution can by no means be satisfactorily explained either by the similarity or diversity of the soil, by thermal relations, or by meteorological conditions. I have long since directed attention to the fact, that the southern hemisphere possesses, for instance, many plants of the natural family of the Rosaceæ, but not a single species of the genus Rosa itself. Claude Gay informs us, that the Rosa Chilensis, described by Meyen, is a variety that has become wild of the Rosa centifolia, Linn., which has been naturalized in Europe for thousands of years. Such wild-growing varieties occupy large tracts in Chili near Valdivia and Osorno.[^[PH]]

In the whole tropical region of the northern hemisphere we only found one single indigenous rose, our Rosa Montezumæ, and this was on the Mexican highland, near Moran, at a height of 9336 feet. We may count among the strange phenomena observed in the distribution of plants, the total absence of the Agave from Chili, though it possesses Palms, Pourretias, and many species of Cactus; and although A. americana flourishes luxuriantly in Roussillon, at Nice, at Botzen, and in Istria, where it was probably introduced from the New Continent since the sixteenth century, and where it forms one connected line of vegetation from the north of Mexico, across the isthmus of Panama, as far as Southern Peru. With respect to the Calceolarias, I long believed that, like the roses, they were only to be found exclusively on the northern side of the equator. In fact, among the twenty-two species that we brought with us, not one was gathered to the north of Quito and the volcano of Pichincha; but my friend Professor Kunth remarks that Calceolaria perfoliata, which Boussingault and Capt. Hall found near Quito, advances also as far as New Granada, and that this species, as well as C. integrifolia, was sent by Mutis from Santa Fé de Bogotá to the great Linnæus.

The species of Pinus, which are so abundant in the wholly inter-tropical Antilles, as well as in the tropical mountain regions of Mexico, do not cross the isthmus of Panama, and are wholly wanting in the equally mountainous parts of tropical South America, that lie north of the equator; they are equally unknown on the elevated plains of New Granada, Pasto, and Quito. I have advanced in the plains and on the mountains from the Rio Sinu, near the isthmus of Panama, as far as 12° south lat.; and in this territorial extent, of nearly 1600 miles in length, the only forms of needle-leaved trees that I saw, were the taxoid Podocarpus (P. taxifolia), 64 feet high, in the Andes pass of Quindiu and in the Paramo de Saraguru, in 4° 26′ north and 3° 40′ south latitude, and an Ephedra (E. americana) near Guallabamba, north of Quito.

Among the group of the Coniferæ, the following are common to the northern and southern hemispheres: Taxus, Gnetum, Ephedra, and Podocarpus. Long before l’Heritier, the last genus had been very properly distinguished from Pinus by Columbus on the 25th of November, 1492. He says, “Pinales en la Serrania de Haiti que no llevan piñas, pero frutos que parecen azeytunos del Axarafe de Sevilla.”[^[PI]] Species of yew extend from the Cape of Good Hope to 61° north lat. in Scandinavia, consequently through more than 95 degrees of latitude. Podocarpus and Ephedra are almost as widely distributed; and even from among the Cupuliferæ, the species of the oak genus, usually termed by us a northern form, though they do not cross the equator in South America, reappear in the southern hemisphere, at Java, in the Indian archipelago. To this latter hemisphere ten genera of the cone-bearing trees exclusively appertain, of which we will here cite only the most important: Araucaria, Dammara (Agathis, Sal.), Frenela (comprising about 18 Australian species), Dacrydium and Lybocedrus, whose habitat is both in New Zealand and the Straits of Magellan. New Zealand possesses one species of the genus Dammara (D. australis), but no Araucaria. The contrary, by a singular contrast, is the case in New Holland.

In the form of acicular-leaved trees, Nature presents us with the greatest length of stem existing in arborescent productions. I use the term arborescent, for, as we have already remarked, among the Laminariæ (the oceanic algæ) Macrocystis pyrifera, between the coast of California and 68° south lat., often attains a length of more than 400 feet. If we exclude the six Araucarias of Brazil, Chili, New Holland, the Norfolk Islands and New Caledonia, then those Coniferæ are the highest, whose habitat is the temperate zone of the North. As we have found among the family of the palms the most gigantic of all, the Ceroxylon andicola, about 192 feet high, in the temperate Alpine climate of the Andes, so in like manner do the loftiest cone-bearing trees belong, in the northern hemisphere, to the temperate north-western coast of America and to the Rocky Mountains (lat. from 40° to 52°), in the southern hemisphere to New Zealand, Tasmania or Van Dieman’s Land, to Southern Chili and Patagonia, (where the lat. is again from 43° to 50°). The most gigantic forms among the genus Pinus are Sequoia (Endl.), Araucaria, and Dacrydium. I only name those species whose height not merely reaches but often exceeds 200 feet. That the reader may have a standard of comparison, he is reminded that in Europe the loftiest Red and White Pines, especially the latter, reach a height of from 160 to 170 feet; for instance, in Silesia, the pine in the Lampersdorf forest, near Frankenstein, long famous for its altitude, is only 158 feet high, although 17 feet in girth.[^[PJ]]

We give the following examples:—

Pinus Grandis (Dougl.), in New California, attains a height of 202–224 feet.

Pinus Frémontiana (Endl.), also there, and probably of the same height.[^[PK]]

Dacrydium Cupressinum (Solander), in New Zealand, above 213 feet.

Pinus Lambertiana (Dougl.), in North-western America, 223–234 feet.

Araucaria Excelsa (R. Brown), the Cupressus columnaris of Forster, in Norfolk Island and the surrounding rocks, 182–223 feet. The six Araucariæ hitherto known fall into two groups, according to Endlicher:

α. The American (Brazil and Chili), A. brasiliensis [Rich.], between 15° and 25° south lat., and A. imbricata [Pavon], between 35° and 50° south lat.; the latter 234–260 feet;

β. The Australian (A. Bidwilli [Hook.] and A. Cunninghami [Ait.] on the eastern side of New Holland, A. excelsa of Norfolk Island, and A. Cookii [R. Brown] of New Caledonia). Corda, Presl, Göppert, and Endlicher have already found five fossil Araucariæ in lias, in chalk, and in lignite.[^[PL]]

Pinus Douglasii (Sab.) in the valleys of the Rocky Mountains and at the Columbia River (north lat. 43°–52°). That meritorious Scotch botanist, whose name this tree bears, suffered a dreadful death in 1833, when he came from New California to collect plants on the Sandwich Islands. He inadvertently fell into a pit, into which one of the wild bulls of that country, always viciously disposed, had previously fallen. This traveller has described from accurate measurements a stem of P. Douglasii, which at three feet from the ground was 57½ feet round, and 245 feet high.[^[PM]]

Pinus Trigona (Rafinesque), on the western slope of the Rocky Mountains.[^[PN]] This “gigantic fir” was measured with great care; the girth of the stem at 6¼ feet above the ground was often from 38 to 45 feet. One stem was 300 feet high, and without branches for the first 192 feet.

Pinus Strobus (in the eastern part of the United States of North America, especially on this side of the Mississippi, but also again in the Rocky Mountains, from the source of the Columbia to Mount Hood, from 43° to 54° north lat.), in Europe called the Weymouth Pine, and in North America the White Pine, commonly no more than 160 to 190 feet high, but several have been seen in New Hampshire of 250 and 266 feet.[^[PO]]

Sequoia Gigantea (Endl.; the Condylocarpus, Sal.), of New California, like the Pinus trigona, about 300 feet high.

The nature of the soil and the conditions of heat and moisture, on which the nourishment of plants simultaneously depends, promote, it must be admitted, the development and the increase of the number of the individuals in a species; but the gigantic height attained by the stems of a few among the many nearly allied species of the same genus is not dependent on soil and climate but on a specific organization, on internal natural disposition, common alike to the vegetable and to the animal world. With the Araucaria imbricata of Chili, the Pinus Douglasii of the Columbia River, and the Sequoia gigantea of New California (245–300 feet) contrasts most strongly—not the Willow (Salix arctica) stunted by cold or mountain height, and only two inches high,—but a little phanerogamic plant in the beautiful climate of the southern tropical region, in the Brazilian province of Goyaz. The moss-like Tristicha hypnoides, of the Monocotyledonous family of the Podostemeæ, hardly attains the height of three lines. “While crossing the Rio Clairo in the province of Goyaz,” says an excellent observer, “I perceived on a stone a plant, the stalk of which was not more than three lines high, and which I considered at first to be a moss. It was, however, a phanerogamic plant, supplied with sexual organs like our oaks, and those gigantic trees which raised their majestic heads around.”[^[PP]]

Besides the height of the stem, the length, breadth, and position also of the leaves and fruit, the aspiring or horizontal, almost umbellate ramification, the gradation of the colour from fresh or silver-greyish green to dark brown, give a peculiar physiognomical character to the Coniferæ. The acicular leaves of Pinus Lambertiana (Douglas) in North-Western America are five, those of the P. excelsa (Wallich) on the southern slope of the Himalaya near Katmandu, seven, and those of P. longifolia (Roxb.) on the mountain range of Cashmere, more than twelve inches long. Moreover, in one and the very same species, these acicular leaves vary in the most remarkable manner, from the combined influence of the nourishment derived from soil and air, and of the height above the level of the sea. I found these variations in the length of the leaves of our common wild pine (Pinus sylvestris) so great, while travelling in a west and east direction over an extent of 80° of longitude (more than 3040 miles) from the Scheldt, through Europe and Northern Asia, to Bogoslowsk, in the Northern Ural, and Barnaul beyond the Obi, that occasionally, deceived by the shortness and rigidity of the leaves, I have mistaken it for another species of pine, allied to the mountain fir, P. rotundata, Link, (Pinus uncinata, Ram.) These are, as Link correctly observes,[^[PQ]] transitions to Ledebour’s P. sibirica of the Altai.

The delicate and pleasing green though deciduous foliage of the Ahuahuete (Taxodium distichum, Rich., Cupressus disticha, Linn.) on the Mexican plateau especially delighted me. In this tropical region the tree, swelling out to a portly bulk, and the Aztec name of which signifies “water-drum” (from atl, water, and huehuetl, drum), flourishes from 5750 to 7670 above the level of the sea, whilst it descends towards the plain in the marshy district (Cypress swamps) of Louisiana as far as 43° lat. In the southern States of North America the Taxodium distichum (Cyprès chauve), as well as in the lofty plains of Mexico, attains a height of 128 feet, with an enormous girth, the diameter being from 30 to nearly 40 feet, when measured near the ground.[^[PR]] The roots, too, present a very remarkable phenomenon, for they have woody excrescences, which are sometimes of a conical and rounded, sometimes of a tabular shape, and project three and even nearly five feet above the ground. Travellers have compared these woody excrescences, in spots where they are numerous and frequent, to the grave-tablets of a Jewish churchyard. Auguste de St. Hilaire remarks, with much acuteness: “These excrescences of the bald cypress, which resemble boundary-posts, may be regarded as exostoses, and like these live in the air; adventitious buds would doubtless escape from them, if the nature of the tissue of the coniferous plants did not oppose itself to the development of those concealed germs that give birth to these kinds of buds.”[^[PS]] In addition to the above, a remarkably enduring vitality is manifested in the roots of cone-bearing trees by the phenomenon which, under the name of “Effervescence,” (aftergrowth?) has attracted, in many ways, the attention of botanical physiologists, and which phenomenon, it appears, rarely displays itself in other dicotyledonous plants. The stumps of the felled white Pine, left in the ground, form, during a succession of several years, new layers of wood, and continue to increase in thickness, without throwing out shoots, branches, or leaves. The excellent observer Göppert believes, that this takes place solely through nourishment derived from the roots, which the extremity of the stem receives from a neighbouring living tree of the same species. The roots of the living tree he conceives are organically incorporated with those of the stump.[^[PT]] Kunth, in his excellent new Lehrbuch der Botanik, is opposed to this explanation of a phenomenon, which was even known, though imperfectly, to Theophrastus.[^[PU]] According to him, this process is perfectly analogous to that by which metallic plates, nails, carved letters, nay, even stags’ horns become imbedded within the body of wood. “The cambium, that is, the thin, walled cellular tissue, conducting muco-granular sap, from which new formations alone proceed, continues without any relation to the buds (being perfectly independent of them) to deposit new layers of wood on the outermost layer.”[^[PV]]

The relation above alluded to, between the absolute height of the ground and the geographical as well as isothermal latitude, shows itself often, no doubt, when one compares the arborescent vegetation of the tropical part of the Andes chain with the vegetation of the north-west coast of America, or the banks of the Canadian lakes. The same remark was made by Darwin and Claude Gay in the southern hemisphere, when they, in their descent from the plateau of Chili, advanced towards Eastern Patagonia, and the Archipelago of Tierra del Fuego; here woods of Drymis Winteri, together with Fagus antarctica and Fagus Forsteri, cover every thing with long uniform rows in a northern and southern direction down to the low lands. Trifling deviations from the law of constant station-ratios between mountain height and geographical latitude, depending or local causes, not sufficiently investigated, occur even in Europe. I would call to mind the limits of altitude for the birch and common fir in a part of the Swiss Alps, on the Grimsel. The fir (Pinus sylvestris) flourishes there up to 6330; and the birch (Betula alba) up to 6906 feet; beyond them again there is a belt of stone pines (Pinus cembra), whose upper boundary is 7343 feet. The birch, in consequence, lies there between two belts of Coniferæ. According to the excellent observations of Leopold von Buch, and the more recent ones of Martius, who also visited Spitzbergen, the limits of the geographical distribution in the high Scandinavian north (in Lapland) are as follows: “The Fir extends to 70°; the White Birch (Betula alba) to 70° 40′; the Dwarf-Birch (B. nana) to 71° at least: Pinus cembra is entirely wanting in Lapland.”[^[PW]]

As the length and the position of the acicular leaves define the physiognomic character of the coniferæ, this is still more designated by the specific difference of the leaf-breadth, and the parenchymatous development of the appendicular organs. Several species of Ephedra may be said to be almost leafless; but in Taxus, Araucaria, Dammara, (Agathis), and the Salisburia adiantifolia of Smith (Gingko biloba, Linn.), the breadth of the leaf gradually increases. I have here arranged the genera morphologically. Even the names of the species, as first chosen by botanists, indicate such an arrangement. Dammara orientalis of Borneo and Java, often 11 feet in diameter, was at first named loranthifolia: Dammara australis (Lamb.), in New Zealand, rising to 150 feet high, was originally named zamæfolia. Neither of these has acicular leaves, but “folia alterna oblongo lanceolata, opposita, in arbore adultiori sæpe alterna, enervia, striata.” The lower surface of the leaf is densely covered with stomata. These transitions of the appendicular system, from the greatest contraction to a broad leaf surface, possess, like every advance from simple to compound, both a morphological and a physiognomical interest.[^[PX]] The short-stalked, broad, split leaf of the Salisburia (Kämpfer’s Ginkgo), has also the breathing pores (stomata) only on the inferior side. The original habitat of the tree is not known. It became distributed from the Chinese temples to the gardens of Japan, in consequence of the intercourse that existed in olden times between the congregations of Buddha.

I was a witness of the singularly painful impression, which the first sight of a pine-forest at Chilpanzingo made on one of our companions in travelling from a port in the South Sea through Mexico to Europe. Born in Quito, under the equator, he had never seen needle-leaved trees and folia acerosa. The trees appeared to him to be leafless, and because we were journeying towards the cold north, he thought he recognised already, in the extreme contraction of the organs, the impoverishing influence of the Pole. The traveller, whose impressions I am here describing, and whose name neither Bonpland nor myself can mention without regret, was an excellent young man, the son of the Marquis de Selvalegre, Don Carlos Montufar, whose noble and ardent love of freedom courageously led him, a few years later, to a violent, though not dishonourable, death, in the war of independence, waged by the Spanish colonies.

[94]. p. 227—“Pothos plants, Aroideæ.”

Caladium and Pothos are forms appertaining exclusively to the tropical world, whilst the different species of Arum belong more to the temperate zone. Arum italicum, A. dracunculus, and A. tenuifolium advance as far as Istria and Friuli. No Pothos has hitherto been discovered in Africa. The East Indies possess several species of this genus (P. scandens and P. pinnata), which have a less beautiful physiognomy and are of less luxuriant growth than the American Pothos plants. We discovered a beautiful true arborescent Aroidea (Caladium arboreum), having a stem from 16 to more than 21 feet in height, near the convent of Caripe, east of Cumana. Beauvois found a singular Caladium (Culcasia scandens) in the kingdom of Benin.[^[PY]] In the Pothos form the parenchyma occasionally expands to so great a degree that the leaf-surface becomes perforated with holes, as in Calla pertusa (Kunth), and Dracontium pertusum (Jacquin), which we collected in the forests of Cumana. It was the Aroideas which first drew attention to the remarkable phenomenon of the fever-heat evolved by certain plants during the period of their inflorescence, and which even sensibly affects the thermometer, and is connected with a great and temporary increase in the absorption of oxygen from the atmosphere. Lamarck, in 1789, observed this increase of temperature in the Arum italicum. According to Hubert and Bory de St. Vincent, the vital heat of the Arum cordifolium rises in the Isle of France to 110° or 120°, whilst the temperature of the surrounding air is only 66°.2 Fahr. Even in Europe, Becquerel and Breschet found a difference of 39°.4. Dutrochet observed a paroxysm,—a rhythmical decrease and increase of vital heat,—which appeared by day to attain a double maximum. Théodore de Saussure remarked analogous augmentations of heat, although only of 1°.1 and 1°.8 Fahr., in other families of plants; as, for instance, in Bignonia radicans and Cucurbita pepo. In the latter, the male plant exhibited a greater increase of temperature than the female, when measured by a very sensitive thermoscopic apparatus. Dutrochet—whose early death is greatly to be regretted, on account of the important services he rendered to physics and vegetable physiology—likewise observed,[^[PZ]] by means of thermo-magnetic multiplicators, a vital heat of 0°.25 to 0°.67 Fahr. in many young plants (Euphorbia lathyris, Lilium candidum, Papaver somniferum), and even among funguses, in many species of Agaricus and Lycoperdon. This vital heat disappeared at night, but not by day, even when the plants were placed in the dark.

The contrast presented by the physiognomy of the Casuarineas, acicular-leaved trees, and the almost leafless Peruvian Colletias and Pothos plants (Aroideas), is still more striking when we compare these types of extreme contraction in the leaf form with Nymphæaceæ and Nelumboneæ. Here we again meet, as in the Aroideæ, with leaves in which the cellular tissue is excessively expanded upon long, fleshy, succulent petioles,—as Nymphæa alba, N. lutea, N. thermalis (formerly called N. lotus, from the hot spring of Pecze, near Groswardein in Hungary), the species of Nelumbo, Euryale amazonica (Pöppig), and Victoria Regina, allied to the prickly Euryale, although of a very different genus, according to Lindley, and discovered in 1837 by Sir Robert Schomburgk in the river Berbice, in British Guiana. The round leaves of this splendid aquatic plant are from 5 to 6 feet in diameter, and surrounded by upright margins from 3 to 5 inches in height, which are light green on the inner side, but of a bright crimson on the outside. These agreeably perfumed flowers, of which 20 or 30 may be seen together in a small space, are about 15 inches in diameter, of a white or rose colour, and have many hundred petals.[^[QA]] Pöppig also gives to the leaves of his Euryale amazonica, which he found at Tefé, a diameter of about 6 feet.[^[QB]] Whilst Euryale and Victoria present a greater parenchymatous expansion of the leaf-form in all its dimensions than other genera, the most gigantic development of the blossoms occurs in a parasitical Cytinea, which Dr. Arnold discovered in Sumatra in 1818. This flower, Rafflesia Arnoldi (R. Brown), has a stemless blossom measuring three feet in diameter, surrounded by large leaf-like scales. Like funguses, it has an animal odour, and smells something like beef.

[95]. p. 227—“Lianes, Creeping Plants, (Span. Vejuccos.)”

According to Kunth’s division of Bauhinias, the true genus Bauhinia belongs to the New Continent. The African Bauhinia, B. rufescens (Lam.), is a Pauletia (Cav.), a genus of which we also discovered some new species in South America. In the same manner the Banisterias of the Malpighiaceæ are actually an American form. Two species are indigenous to the East Indies, and one—described by Cavanilles as B. leona—to Western Africa. In the tropical zone, and in the Southern hemisphere, species of the most different families belong to the climbing plants which in those regions render the forests so impenetrable to man and so accessible and habitable to the whole monkey family (Quadrumana), the Cercoleptes, and the small tiger cats. The Lianes thus afford whole flocks of gregarious animals an easy means of rapidly ascending high trees, passing from one tree to another, and even of crossing brooks and rivulets.

In the south of Europe and in the north of America, Hops from the Urticeæ, and the species of Vitis from the Ampelideæ, belong to Climbing Plants; while this form is represented in the tropics by climbing and trailing grasses. We found on the elevated plains of Bogota, in the pass of Quindiu in the Andes, and in the Cinchona forests of Loxa, a Bambusa allied to Nastus, our Chusquea scandens, twined round powerful trunks of trees, adorned at the same time with flowering Orchideæ. Bambusa scandens (Tjankorreh), which Blume found in Java, belongs probably to Nastus, or to the grass-genus Chusquea, the Carrizo of the Spanish settlers. In the pine forests of Mexico, Climbing Plants seem to be entirely wanting; but in New Zealand a fragrant Pandanus, Freycinetia Banksii, together with one of the Smilaceæ, Ripogonum parviflorum (R. Brown), which renders the forests almost impenetrable, winds round a gigantic fir-tree more than 200 feet high, Podocarpus dacryoides (Rich.), called Kakikatea in the language of the country.[^[QC]]

A striking contrast to these Climbing Grasses and Creeping Pandaneas is afforded by the splendid many-coloured blossoms of the Passion flowers (among which, however, we ourselves found one arborescent, upright, species (Passiflora glauca) in the Andes of Popayan, at an elevation of nearly 10,500 feet, and by the Bignoniaceæ, Mutisiæ, Alströmeriæ, Urvilleæ, and Aristolochiæ. Among the latter, our Aristolochia cordata has a coloured (purplish red) calyx, about seventeen inches in diameter; “flores gigantei, pueris mitræ instar inservientes.” Owing to the quadrangular form of their stalks, their flattening, which is not occasioned by any external pressure, and a band-like undulatory motion, many of these climbing plants have a peculiar physiognomy. The diagonal intersections of the stems of Bignonias and Banisterias form, by means of furrows in the ligneous substance, and through its clefts, where the bark penetrates to some depth, cruciform or mosaic-like figures.[^[QD]]

[96]. p. 228—“The form of Aloes.”

To this group of plants, which is characterised by a great similarity, belong Yucca aloifolia, which penetrates as far north as Florida and South Carolina; Y. angustifolia (Nutt.), which advances to the banks of the Missouri; Aletris arborea; the Dragon-tree of the Canaries, and two other Dracænas belonging to New Zealand; arborescent Euphorbias; and Aloe dichotoma, Linn., (formerly the genus Rhipidodendrum of Willdenow), the celebrated Koker-boom, whose stem is four feet in thickness, about twenty feet high, and has a crown measuring 426 feet round.[^[QE]] The forms which I have here associated together belong to very different families: as, for instance, to the Liliaceæ, Asphodeleæ, Pandaneæ, Amaryllideæ, and Euphorbiaceæ; and are therefore, with the exception of the last named, all included under the great division of Monocotyledons. One of the Pandaneæ, Phytelephas macrocarpa (Ruiz), which we found on the banks of the Magdalena river in New Granada, exactly resembles with its feathery leaves a small palm-tree. The Tagua (as it is called by the Indians) is moreover, as Kunth has observed, the only Pandanea of the New Continent. The singular Agave-like and high-stemmed Doryanthes excelsa of New South Wales, which the intelligent Correa de Serra was the first to describe, belongs to the Amaryllideæ, like our low-growing Narcissuses and Jonquils.

In the candelabra-like form of Aloes, the branches of the main-trunk must not be confounded with the flower-stalks. In the American aloe, Agave Americana (Maguey de Cocuyza), which is entirely wanting in Chili, and in the Yucca acaulis (Maguey de Cocuyza), the leaf-stalks present a candelabra-like arrangement of the blossoms during the excessively rapid and gigantic development of the inflorescence, which, as is well known, is but too transient a phenomenon. In some arborescent Euphorbias the physiognomical character depends, however, on the branches and their arrangement. Lichtenstein describes,[^[QF]] with much animation, the impression made upon him by the appearance of an Euphorbia officinarum which he saw in the “Chamtoos Rivier,” near Cape Town. The form of the tree was so symmetrical, that it repeated itself on a small scale, like a candelabrum, to a height of more than 30 feet. All the branches were furnished with sharp thorns.

Palms, Yucca and Aloe plants, arborescent Ferns, some Aralias, and the Theophrasta, where I have seen it in a state of luxuriant growth, present to the eye a certain physiognomical resemblance of character by the nakedness of the stems (there being no branches) and the beauty of their summits or crowns, however they may otherwise differ in the structure of the inflorescence.

Melanoselinum decipiens, (Hofm.), which has been introduced into our gardens from Madeira, and is sometimes from 10 to 12 feet high, belongs to a peculiar group of arborescent umbelliferæ allied to the Araliaceæ, to which other species, as yet undiscovered, will undoubtedly at some future time be added. Ferula, Heracleum, and Thapsia likewise attain a considerable height, but they are still herbaceous shrubs. Melanoselinum stands almost entirely alone as an arborescent umbelliferous plant; Bupleurum (Tenoria) fruticosum, Linn., of the shores of the Mediterranean, Bubon galbanum of the Cape, and Crithmum maritimum of our sea-coasts, are only shrubs. Tropical countries, where, as Adanson long since very correctly remarked, Umbellifereæ and Crucifereæ are almost wholly wanting in the plains, exhibit, as we ourselves observed, the most dwarfish of all the umbelliferous family on the lofty mountain ridges of the South American and Mexican Andes. Among the thirty-eight species which we collected on elevations whose mean temperature was below 54°.5 Fahr., we found Myrrhis andicola, Fragosa arctioïdes, and Pectophytum pedunculare, interspersed with an equally dwarfish Alpine Draba, growing moss-like close to the rock and the frequently frozen earth, at a height of 13,428 feet above the level of the sea. The only tropical umbelliferous plants which we found on the plain in the New Continent were two species of Hydrocotyle (H. umbellata and H. leptostachya) between the Havannah and Batabano, and therefore at the extreme limit of the torrid zone.

[97]. p. 228—“The form of Grasses.”

The group of the arborescent grasses which Kunth has collected under the head of Bambusaceæ, in his great work on the plants collected by Bonpland and myself, constitutes one of the most beautiful adornments of tropical vegetation. Bambu, called also Mambu, occurs in the Malay language, although according to Buschmann merely as an isolated expression, the ordinary term in use being buluh, whilst the only name for this species of cane in Java and Madagascar is wuluh, voulou. The numbers of the genera and species included in this group have been extraordinarily increased by the industry of botanical travellers. It has been found that the genus Bambusa is entirely wanting in the New Continent, to which region, however, the gigantic Guaduas, discovered by us, and which attain a height of from 50 to 64 feet, together with the Chusquea, exclusively belong; that Arundinaria (Rich.) occurs in both continents, although differing specifically in each; that Bambusa and Beesha (Rheed.), occur in India and the Indian Archipelago; and that Nastus grows in the islands of Madagascar and Bourbon. With the exception of the high-climbing Chusquea, these forms morphologically replace each other in different parts of the earth. In the northern hemisphere far beyond the limits of the torrid region, in the valley of the Mississippi, the traveller is gladdened by the sight of a species of Bamboo, the Arundinaria macrosperma, formerly called also Miegia and Ludolfia. In the southern hemisphere, in the south of Chili, between the parallels of 37° and 42°, Gay found one of the Bambusaceæ more than 20 feet high (not a climbing, but a still undescribed arborescent self-supporting Chusquea), growing, mingled with Drymis Chilensis, in a region clothed with an uniform forest-covering of Fagus obliqua.

Whilst in India the Bambusa flowers so frequently that in Mysore and Orissa the seeds are mixed with honey, and eaten like rice,[^[QG]] in South America the Guadua blossoms so very seldom that in the course of four years we were only twice able to procure the flowers; once on the solitary banks of the Cassiquiare, the arm connecting the Orinoco with the Rio Negro and the Amazon, and again in the province of Popayan, between Buga and Quilichao. It is a very striking fact that some plants grow with the greatest vigour in certain localities without flowering; as is the case with the European olive-trees introduced into America centuries ago, and growing between the tropics, near Quito, at elevations of about 9600 feet above the level of the sea; and in like manner the walnuts, hazel-nut bushes, and the fine olive-trees (Olea Europea) of the Isle of France.[^[QH]]

As some of the Bambusaceæ (arborescent grasses) advance into the temperate zone, so also they do not suffer in the torrid zone from the temperate climate of mountain districts. They are certainly more luxuriant as social plants between the sea-shore and elevations of about 2558 feet in the Province de las Esmeraldas, west of the volcano of Pichincha, where Guadua angustifolia (Bambusa Guadua of our Plantes équinoxiales, t, i. tab. xx) generates in its interior large quantities of the siliceous Tabaschir (Sanscrit tvakkschira, cow-milk). We saw the Guadua advance in the pass of Quindiu, in the chain of the Andes, to a height of 5755 feet above the level of the sea, as determined by barometric measurements. Nastus borbonicus has been called a true Alpine plant by Bory de St. Vincent, and according to him it does not descend lower than 3840 feet on the declivity of the volcano in the island of Bourbon. This appearance or the repetition at great elevations of certain forms belonging to torrid plains calls to mind the group of Alpine palms (Kunthia montana, Ceroxylon andicola, and Oreodoxa frigida) of which I have already spoken, and a grove of Musaceæ (Heliconia, perhaps Maranta), 16 feet high, which I found growing isolated on the Silla de Caracas, at a height of more than 7000 feet above the level of the sea.[^[QI]] While the form of gramineæ, with the exception of some few herbaceous dicotyledons, constitutes the highest phanerogamic zone on the snow-crowned summits of mountains, so the grasses mark the boundary of phanerogamic vegetation in a horizontal direction, towards the northern and southern polar regions.

Many admirable general results, no less than a great mass of important materials, have been yielded to the geography of plants by my young friend, Joseph Hooker, who, after having but recently returned with Sir James Boss from the frozen antarctic regions, is now engaged in exploring the Thibetian Himalaya. He draws attention to the fact that phanerogamic flowering plants (grasses) advance 17½° nearer to the north than to the south pole. In the Falkland Islands, near the thick knots of Tussac grass, Dactylis cæspitosa, Forster. (a Festuca, according to Kunth), and in Tierra del Fuego, under the shade of the birch-leaved Fagus antarctica, there grows the same Trisetum subspicatum, which spreads over the whole range of the Peruvian Andes, and across the Rocky Mountains, to Melville Island, Greenland, and Iceland, and is also found in the Swiss and Tyrolese Alps as well as in the Altai, in Kamtschatka, and in Campbell’s Island, south of New Zealand, extending therefore over 127 degrees of latitude, or from 54° south to 72° 50′ north lat. “Few grasses,” says Joseph Hooker,[^[QJ]] “have so wide a range as Trisetum subspicatum (Beauv.), nor am I acquainted with any other arctic species which is equally an inhabitant of the opposite polar regions.” The South Shetland Islands, which are separated by Bransfield Straits from d’Urville’s “Terre de Louis-Philippe” and from Peak Haddington, a volcano, 7046 feet high, and situated in 64° 12′ south lat., have recently been visited by Dr. Eights, a botanist from the United States. He found there (probably in 62° or 62¼° south lat.) a small grass, Aira antarctica,[^[QK]] which is “the most antarctic flowering plant hitherto discovered.”

Even in Deception Island, belonging to the same group, 62° 50′, only lichens are met with, and no longer any species of grass; and in like manner further south-east, in Cockburn’s Island (64° 12′) near Palmer’s Land, only Lecanoras, Lecideas, and five foliaceous Mosses, among which is our German Bryum argenteum, were gathered. “This appears to be the Ultima Thule of antarctic vegetation,” for further south even terrestrial cryptogamia are wanting. In the great bay formed by Victoria Land, on a small island lying opposite to Mount Herschel (in 71° 49′ lat.), and on Franklin Island, 92 miles north of the volcano, Erebus, (12,366 feet in height), and in 76° 7′ south lat., Hooker found no trace of vegetation. In extreme northern latitudes, the distribution of even the higher organisms is very different; for here phanerogamic plants advance 18½° nearer to the pole than in the southern hemisphere. Walden Island (80½° north lat.) possesses still ten species of phanerogamia. Antarctic phanerogamic vegetation is also poorer in species at equal distances from the pole; thus Iceland has five times more phanerogamia than the southern group of Auckland and Campbell Islands, but the uniform vegetation of the antarctic regions is, from climatic causes, both more succulent and more luxuriant.[^[QL]]

[98]. p. 229—“Ferns.”

If we estimate the whole number of the cryptogamia hitherto described at 19,000 species, as has been done by Dr. Klotzsch, a naturalist possessing a profound acquaintance with the Agamic plants, we shall have for Fungi 8000 (of which Agarici constitute the eighth part); for Lichens, according to J. von Flotow of Hirschberg, and Hampe of Blankenburg, at least 1400; for the Algæ 2580; for Mosses and Liverworts, according to Carl Müller of Halle, and Dr. Gottsche of Hamburgh, 3800; and for Ferns 3250. For this last important result we are indebted to the profound investigations made by Professor Kunze of Leipzig, on this group of plants. It is a striking fact that the family of the Polypodiaceæ alone includes 2165 of the whole number of described Filices, whilst other forms, as the Lycopodiacæ and Hymenophyllaceæ, number only 350 and 200. There are therefore nearly as many described species among Ferns as among Grasses.

It is singular that no mention of the beautiful arborescent ferns is to be found in the classic authors of antiquity, Theophrastus, Dioscorides, and Pliny; while, from the information given by the companions of Alexander, Aristobulus, Megasthenes, and Nearchus, reference is made [^[QM]] to Bamboos, “quæ fissis internodiis lembi vice vectitabant navigates;” to the Indian trees “quarum folia non minora clypeo sunt;” to the Fig-tree which takes root from its branches, and to Palms, “tantæ proceritatis, ut sagittis superjici nequeant.” I find the first mention of arborescent ferns in Oviedo.[^[QN]] “Among ferns,” says this experienced traveller, who had been appointed by Ferdinand the Catholic, Director of the Goldwashings in Haiti, “there are some which I class with trees, because they are as thick and high as Pine-trees. (Helechos que yo cuento por arboles, tan gruesos como grandes pinos y muy altos). They mostly grow among the mountains and where there is much water.” This estimate of their height is exaggerated, for in the dense forests near Caripe even our Cyathea speciosa only attains a height of 32 to 37 feet; and an admirable observer, Ernst Dieffenbach, did not see in the most northern of the three islands of New Zealand any trunks of Cyathea dealbata exceeding 42½ feet. In the Cyathea speciosa and the Meniscium of the Chaymas missions, we observed in the midst of the most shady part of the primeval forest, that the scaly stems of some of the most luxuriantly developed of these trees were covered with a shining carbonaceous powder, which appeared to be owing to a singular decomposition of the fibrous parts of the old leaf stalks.[^[QO]]

Between the tropics, where, on the declivities of the Cordilleras, climates are superimposed in strata, the true region of arborescent ferns lies between about 3200 and 5350 feet above the level of the sea. In South America and in the Mexican highlands they seldom descend lower towards the plains than 1280 feet. The mean temperature of this happy region is between 64°.6 and 70°.8 Fahr. It reaches the lowest stratum of clouds (which floats the nearest to the surface of the sea and the plain), and it therefore enjoys uninterruptedly a high degree of humidity, together with a great equality in its thermal relations.[^[QP]] The inhabitants, who are of Spanish descent, call this region “Tierra templada de los helechos.”

The Arabic designation for ferns is feledschun, filix, (from which the f has been changed, according to Spanish usage, into h,) and perhaps the term may be connected with the verb faladscha, “it divides,” from the finely cut margin of the frond.[^[QQ]]

The conditions of genial mildness in an atmosphere charged with aqueous vapour and of great uniformity in respect to moisture and warmth, are fulfilled on the declivities of the mountains in the valleys of the Andes, and more especially in the southern milder and more humid hemisphere, where arborescent ferns advance not only to New Zealand and Van Diemen’s Land (Tasmania), but even as far as the Straits of Magellan and Campbell Island, and therefore to a southern latitude almost identical in degrees with the parallel in which Berlin is situated north of the equator. From among the family of arborescent ferns there flourishes the vigorous Dicksonia squarrosa, in 46° south lat. in Dusky Bay, New Zealand; D. antarctica of Labillardière in Tasmania; a Thyrsopteris in the Island of Juan Fernandez; an undescribed Dicksonia, whose stem is from 12 to 16 feet high, near Valdivia in Southern Chili; and a Lomaria, somewhat less in height, in the Straits of Magellan. Campbell Island is still nearer to the south pole, in 52½° lat., but even there the leafless stem of the Aspidium venustum rises to a height of more than four feet.

The climatic relations under which Ferns (Filices) in general flourish, are manifested in the numerical laws of their quotients of distribution. In the plains within the tropical regions of large continents this quotient is, according to Robert Brown, and from more recent investigations on the subject, ¹⁄₂₀ of all the phanerogamia, and in mountainous districts of large continents ⅙ to ⅛. This ratio is quite different on the small islands scattered over the ocean; for here the proportion borne by the number of ferns to the sum total of all the phanerogamic plants increases so considerably, that in the South-Sea Islands the quotient rises to ¼, while in the sporadic islands, St. Helena and Ascension, the number of ferns is almost equal to half of the whole phanerogamic vegetation.[^[QR]] In receding from the tropics (where on the large continents d’Urville estimates the proportional number at ¹⁄₂₀), the relative frequency of ferns decreases rapidly as we advance into the temperate zone. The quotients are for North America and the British Islands ¹⁄₃₅, for France ¹⁄₅₈, for Germany ¹⁄₅₂, for the dry parts of Southern Italy ¹⁄₇₄, for Greece ¹⁄₈₄. The relative frequency again increases considerably towards the frigid north. Here the family of ferns decreases much slower in the number of its species than does that of phanerogamic plants. The luxuriantly aspiring character of the species, and the number of individuals contained in each, augment the deceptive impression of absolute frequency. According to Wahlemberg’s and Hornemann’s catalogues, the relative numbers of the Filices are for Lapland ¹⁄₂₅, for Iceland ¹⁄₁₈, for Greenland ¹⁄₁₂.

Such are, according to our present knowledge, the natural laws that manifest themselves in the distribution of the graceful form of Ferns. But it would seem as if in the family of Ferns, which have so long been regarded as cryptogamic, we had lately acquired evidence of the existence of another natural law,—the morphological law of propagation. Count Leszczyc-Suminski, who happily combines the power of microscopic investigation with a very remarkable artistic talent, has discovered an organisation capable of effecting fructification in the prothallium of ferns. He distinguishes two sexual apparatuses, of which the female portion is situated in hollow ovate cells in the middle of the sporangium, and the male in the ciliated antheridia, or the organs producing spiral threads, which have already been examined by Nägeli. Fructification is supposed to be effected by means of moveable ciliated spiral threads and not by pollen tubes.[^[QS]] According to this view, Ferns would be, as Ehrenberg remarks,[^[QT]] products of a microscopic fructification taking place on the prothallium, which here serves as a fertilizing receptacle, while throughout the whole course of their often arborescent development they would be flowerless and fruitless plants, having a bud-formation. The spores lying as sori on the under side of the frond are not seeds but flower-buds.

[99]. p. 229—“The Liliaceæ.”

Africa is the principal seat of this form; there the greatest diversity obtains; there they form masses and determine the natural character of the region. The New Continent exhibits also, it is true, magnificent Alströmeriæ and species of Pancratium, Hæmanthus, and Crinum. We have enriched the first of these genera with nine, and the second with three species; but these American liliaceous plants are more diffused and of less social habits than the European Irideæ.

[100]. p. 229—“The Willow Form.”

Nearly 150 different species of the main representatives of this form, or rather of the Willow itself, are already known. They cover the northern parts of the earth from the equator to Lapland. Their number and their varieties of form increase between the 46th and 70th degrees of latitude, more especially in that part of northern Europe which has been so remarkably indented by the early revolutions of our planet. I am acquainted with ten or twelve species of inter-tropical Willows, and these, like the Willows of the southern hemisphere, are deserving of special attention. As nature appears to delight in all zones in a wondrous multiplication of certain animal forms, as for instance, Anatidæ (Lamellirostres), and Pigeons; so likewise are Willows, Pines, and Oaks, widely diffused; the latter always exhibiting a similarity in their fruit, although various differences exist in the form of the leaves. In Willows belonging to the most widely different climates the similarity of the foliage, of the ramification, and of the whole physiognomical conformation, is almost greater than in Coniferæ. In the more southern part of the temperate zone, north of the equator, the number of the species of Willows decreases considerably; although (according to the “Flora atlantica” of Desfontaines) Tunis has still its own species, resembling Salix caprea; whilst Egypt, according to Forskäl, numbers five species, from the catkins of whose male blossoms is distilled the remedial agent Moie chalaf (aqua salicis), so much used in the East. The Willow which I saw in the Canaries is also, according to Leopold von Buch and Christian Smith, a peculiar species (S. canariensis), although common to those islands and to Madeira. Wallich’s catalogue of the plants of Nepaul and the Himalaya already gives 13 species belonging to the subtropical zone of the East Indies, and which have in part been described by Don, Roxburgh, and Lindley. Japan has its own species, of which one, S. japonica. (Thunb.), is also met with in Nepaul as an Alpine plant.

There was not, as far as I am aware, any species of Willow known as belonging to the tropical zone before my expedition, with the exception of S. tetrasperma. We collected seven new species, three of them on the plateaux of Mexico, at an elevation of 8500 feet above the level of the sea. Still higher, as for instance on the Alpine plains, between 12,000 and 15,000 feet, which we frequently visited, we saw nothing in the Andes of Mexico, Quito, and Peru, to remind us of the many small creeping Alpine Willows of the Pyrenees, the Alps, or of Lapland (S. herbacea, S. lanata, and S. reticulata). In Spitzbergen, whose meteorological relations have so much analogy with those of the snow-crowned summits of Switzerland and Scandinavia, Martius described two Dwarf-Willows, whose small woody stems and branches trail along the ground, and are so concealed in the turf-bogs that it is with difficulty their diminutive leaves can be discovered under the moss. The Willow species which I found in 4° 12′ south lat., at the entrance of the Cinchona or Peruvian Bark forests, near Loxa in Peru, and which has been described by Willdenow as Salix Humboldtiana, is most widely diffused over the western part of South America. A Beach-Willow (S. falcata), which we discovered on the sandy shores of the Pacific, near Truxillo, is, according to Kunth, probably a mere variety of the former. In like manner the beautiful and frequently pyramidal Willow, which we constantly saw on the banks of the Magdalena river, from Mahates to Bojorque, and which, according to the report of the natives, had only spread thus far within a few years, may also be identical with S. Humboldtiana. At the confluence of the Magdalena with the Rio Opon, we found all the islands covered with Willows, many of which had stems 64 feet high, with a diameter of from only 8 to 10 inches.[^[QU]] Lindley has made us acquainted with a species of Salix belonging to Senegal, and therefore to the equinoctial region of Africa.[^[QV]] Blume also found two species of Willow near the equator in Java, one wild and indigenous in the island (S. tetrasperma), and another cultivated (S. Sieboldiana). I am only acquainted with the two Willows belonging to the south temperate zone, which have been described by Thunberg (S. hirsuta and S. mucronata). They grow interspersed with Protea argentea, which has the same physiognomy as the Willow, and their leaves and young branches constitute the food of the hippopotamus of the Orange River. The family of Willows is entirely wanting in Australia and the neighbouring islands.

[101]. p. 229—“The Myrtle Form.”

The Myrtle is a graceful plant, with stiff, shining, crowded, and generally entire and small leaves marked with dots. Myrtles impart a peculiar character to three regions of the earth, viz., to southern Europe, more especially to the islands composed of calcareous rocks and trachytic stone, which project from the basin of the Mediterranean; to the continent of New Holland, which is adorned with Eucalyptus, Metrosideros, and Leptospermum; and to an inter-tropical region in the Andes of South America, part of which is a low plain, while the remainder lies at an elevation of from 9000 to more than 10,000 feet above the level of the sea. This Alpine region, called in Quito the Paramos, is entirely covered with trees having a Myrtle-like aspect, even though they may not all belong to the Myrtaceæ. At this elevation grow Escalonia myrtilloides, E. tubar, Simplocos Alstonia, species of Myrica, and the lovely Myrtus microphylla, of which we have given a drawing in our Plantes équinoxiales, t. i. p. 21, pl. iv.; it grows on micaceous schist, at an elevation of 10,000 feet on the Paramo de Saraguru, (near Vinayacu and Alto de Pulla,) which is adorned with so many beautiful flowering Alpine plants. M. myrsinoides ascends in the Paramo de Guamani as high as 11,200 feet. By far the greater number of the 40 species of the genus Myrtus which we collected in the equinoctial zone, and of which 37 were undescribed, belong to the plains and the less elevated mountain spurs. We brought only a single species (M. xalapensis) from the mild tropical climate of the mountains of Mexico; but the Tierra templada, in the direction of the Volcano of Orizaba, no doubt possesses many yet undescribed varieties. We found M. maritima near Acapulco, on the very shore of the Pacific.

The Escalloniæ,—among which E. myrtilloides, E. tubar, E. floribunda are the ornaments of the Paramos, and remind us strongly (by their physiognomical aspect) of the myrtle-form,—formerly constituted, together with the European and South American Alpine roses (Rhododendrum and Befaria), with Clethra, Andromeda, and Gaylussacia buxifolia, the family of the Ericeæ. Robert Brown [^[QW]] has arranged them in a special family, which Kunth has placed between the Philadelphiæ and Hamamelideæ. Escallonia floribunda affords by its geographical distribution one of the most striking examples of the relation existing between distance from the equator and vertical elevation above the level of the sea. I would here again borrow support from the testimony of the accurate observer, my friend Auguste de St. Hilaire.[^[QX]] “MM. Humboldt and Bonpland in their expedition discovered Escallonia floribunda in 4° south lat. at an elevation of 8952 feet. I found the same plant in 21° south lat. in Brazil, which although elevated is very much less so than the Andes of Peru. This plant is of common occurrence between 24° 50′ and 25° 55′ in the Campos Geraes, and I also met with it again on the Rio de la Plata in about 35° lat., on a level with the sea.”

The group of the Myrtaceæ,—to which belong Melaleuca, Metrosideros, and Eucalyptus, commonly classed under the general denomination of Leptospermeæ,—produce partially, wherever the true leaves are supplied by phyllodia (petiole-leaves), or where the direction of the leaves is inclined towards the unexpanded petiole, a distribution of streaks of light and shade wholly unknown in our deciduous-leaved forest. We find that the earliest botanical travellers who visited New Holland were astonished at the singular effect thus produced. Robert Brown was the first to show that this phenomenon depends on the vertical direction of the expanded petioles (the phyllodia of Acacia longifolia and Acacia suaveolens), and on the circumstance, that the light, instead of falling on horizontal surfaces, passes between vertical ones.[^[QY]] Morphological laws in the development of the leaves determine the peculiar character of the varying light and shade. “Phyllodia,” says Kunth, “can in my opinion merely occur in families which have compound pinnate leaves; and in fact they have as yet only been met with in Leguminosæ (in the Acacias). In Eucalyptus, Metrosideros, and Melaleuca, the leaves are simple (simplicia), and their edgewise position depends on a half-turn of the leaf-stalk (petiolus); moreover, it must be remarked, that both surfaces of the leaves are of a similar character.” In the scantily shaded forests of New Holland the optical effects here alluded to are the more frequent, since two groups of Myrtaceæ and Leguminosæ, species of Eucalyptus and Acacia, there constitute nearly one-half of all the greyish-green tree vegetation. Moreover, between the bast-layers of Melaleuca, there are formed easily soluble membranes, which force their way outwards, and by their whiteness reminds us of our birch bark.

The sphere of distribution of the Myrtaceæ is very different in the two continents. In the New Continent, and especially in its western parts, this family, according to Joseph Hooker,[^[QZ]] scarcely extends beyond the parallel of 26° north lat., while in the Southern Hemisphere, there are in Chili, according to Claude Gay, ten species of Myrtle and twenty-two of Eugenia, which mixed with Proteaceæ (Embothrium and Lomatia) and with Fagus obliqua, there constitute forests. The Myrtaceæ become more frequent from the 38th degree of south lat.; in the island of Chiloe, where a metrosideros-like species (Myrtus stipularis) forms almost impenetrable underwood, which is there named Tepuales; and in Patagonia to the extremity of Tierra del Fuego in 56° lat. While in Europe the Myrtaceæ do not extend northward further than 46° lat., they penetrate in Australia, Tasmania, New Zealand and the Auckland Islands to 50½° south latitude.

[102]. p. 229—“Melastomaceæ.”

This group comprises the genera Melastoma (Fothergilla and Tococa Aub. and Rhexia (Meriana and Osbeckia), of which we have collected no less than sixty new species in tropical America alone, on both sides of the equator. Bonpland has published a splendid work on the Melastomaceæ, in two volumes, with coloured plates. There are species of Rhexia and Melastoma which ascend in the chain of the Andes, as Alpine or Paramos shrubs, to 9600 and even more than 11,000 feet above the level of the sea; as for instance Rhexia cernua, R. stricta, Melastoma obscurum, M. aspergillare, and M. lutescens.

[103]. p. 229—“The Laurel-form.”

To this form belong Laurus, Persea, the Ocoteæ, so numerous in South America, and,—on account of their physiognomic similarity,—Calophyllum, also the splendidly aspiring Mammea from the Guttiferæ.

[104]. p. 229—“How instructive to the landscape-painter would be a work which should illustrate the leading forms of vegetation.”

In order to define with more distinctness what I have here only briefly referred to, I may be permitted to incorporate the following considerations from my sketch of a history of landscape painting, and of a graphical representation of the physiognomy of plants.[^[RA]]

“All that relates to the expression of the passions and the beauty of the human form has perhaps attained its fullest development in the temperate northern zone under the skies of Greece and Italy. The artist, drawing from the depths of imagination, no less than from the contemplation of beings of his own species, derives the types of historical painting alike from unfettered creation and from truthful imitation. Landscape painting, though scarcely a more imitative art, has a more material basis, and a more earthly tendency. It requires for its development a greater amount of various and distinct impressions, which, when imbibed from external contemplation, must be fertilized by the powers of the mind in order to be presented to the senses of others as a creative work of art. The grander style of heroic landscape-painting is the combined result of a profound appreciation of nature, and of this inward process of the mind.

“Everywhere, in every separate portion of the earth, nature is indeed only a reflex of the whole. The forms of organization recur again and again in different combinations. Even the icy north is cheered for months together by the presence of herbs and large Alpine blossoms covering the earth, and by a mild azure sky. Hitherto landscape painting among us has pursued her graceful labours familiar only with the simpler forms of our native floras, but not therefore without depth of feeling and richness of creative fancy. Dwelling only on the native and indigenous form of our vegetation, this branch of art, notwithstanding that it has been circumscribed by such narrow limits, has yet afforded sufficient scope for highly-gifted painters, such as the Caracci, Gaspar Poussin, Claude Lorraine, and Ruysdael, to produce the happiest and most varied creations of art, by their magical power of managing the grouping of trees, and the effects of light and shade. That progress which may still be expected in art, from a more animated intercourse with the tropical world, and from ideas engendered in the mind of the artist by the contemplation of Nature in her grandest forms, will never diminish the fame of the old masters. I have alluded to this, to recal the ancient bond which unites a knowledge of Nature with poetry and a taste for art. For in landscape painting, as in every other branch of art, a distinction must be drawn between the elements generated by a limited field of contemplation and direct observation, and those which spring from the boundless depth of feeling, and from the force of idealising mental power. The grand conceptions which landscape painting, as a more or less inspired branch of the poetry of nature, owes to the creative power of the mind, are, like man himself, and the imaginative faculties with which he is endowed, independent of place. These remarks especially refer to the gradations in the form of trees from Ruysdael and Everdingen, through the works of Claude Lorraine, to Poussin and Annibal Caracci. In the great masters of art there is no indication of local limitation. But an extension of the visible horizon, and an acquaintance with the nobler and grander forms of nature, and with the luxuriant fulness of life in tropical regions, afford the advantage of not simply enriching the material groundwork of landscape-painting, but also of inducing more vivid impressions in the minds of less highly gifted painters, and thus heightening their powers of artistic creation.”

[105]. p. 230—“From the thick and rough bark of the Crescentiæ and Gustaviæ.”

In Crescentia Cujete (the Tutuma tree, whose large fruit-shells are so indispensable to the natives as household utensils), in Cynometra, the Cacao-tree (Theobroma), and the Perigara Gustavia (Linn.), the tender blossoms burst forth from the half-carbonized bark. When children eat the fruit of the Pirigara speciosa (the Chupo), their whole bodies become tinged with yellow; and this jaundice, after a continuance of from twenty-four to thirty-six hours, disappears without the use of medicine.

An indelible impression was produced on my mind by the luxuriant power of vegetation in the tropical world, when, on entering a Cacao plantation (Caca hual), in the Valles de Aragua, after a damp night, I saw for the first time large blossoms springing from the root of a Theobroma, deeply imbedded in the black soil. This is one of the most instantaneous manifestations of the activity of the vegetative force of organisation. Northern nations speak of “the awakening of Nature at the first genial breath of Spring;”—expressions that strongly contrast with the imaginative complaint of the Stagirite, who regarded vegetable forms as buried in a “still sleep, from which there is no awakening, and free from the desires that excite to spontaneous motion.”[^[RB]]

[106]. p. 230—“Draw on their heads as caps.”

These are the flowers of our Aristolochia cordata, to which reference has been made in Illustration 25. The largest flowers in the world, besides those belonging to the Compositæ (the Mexican Helianthus annuus), are produced by Rafflesia Arnoldi, Aristolochia, Datura, Barringtonia, Gustavia, Carolinea, Lecythis, Nymphæa, Nelumbium, Victoria Regina, Magnolia, Cactus, the Orchideæ, and the Liliaceous forms.

[107]. p. 231—“The luminous worlds which spangle the firmament from pole to pole.”

The more magnificent portion of the southern sky, in which shine the constellations of the Centaur, Argo, and the Southern Cross, where the Magellanic clouds shed their pale light, is for ever concealed from the eyes of the inhabitants of Europe. It is only under the equator that man enjoys the glorious spectacle of all the stars of the southern and northern heavens revealed at one glance. Some of our northern constellations,—as, for instance, Ursus Major and Ursus Minor,—owing to their low position when seen from the region of the equator, appear to be of a remarkable, almost fearful magnitude. As the inhabitant of the tropics beholds all stars, so too, in regions where plains, deep valleys, and lofty mountains are alternated, does Nature surround him with representatives of every form of vegetation.

In the foregoing sketch of a “Physiognomy of Plants,” I have endeavoured to keep in view three nearly allied subjects,—the absolute diversity of forms; their numerical relations, i.e. their local preponderance in the whole number of phanerogamic floras; and their geographical and climatic distribution. If we would rise to a general view regarding vital forms;—the physiognomy, the study of the numerical relations (the arithmetic of botany), and the geography of plants (the study of the local zones of distribution), cannot, as it seems to me, be separated from one another. The study of the physiognomy of plants must not be exclusively directed to the consideration of the striking contrasts of form which the larger organisms present, when considered separately; but it must rise to the recognition of the laws which determine physiognomy of nature generally, the picturesque character of vegetation over the whole surface of the earth, and the vivid impression produced by the grouping of contrasted forms in different zones of latitude and elevation. It is when concentrated into this focus that we first clearly perceive the close and intimate connection existing between the subjects treated of in the preceding pages. We have here entered upon a field of inquiry hitherto but little cultivated. I have ventured to follow the method first propounded with such brilliant results in Aristotle’s zoological works, and which is so especially adapted to establish scientific confidence,—a method in which the incessant effort to arrive at a generalisation of ideas supported by individual illustrations, is associated with an endeavour to penetrate to the specialities of phenomena.

The enumeration of forms is, from the physiognomical difference of their nature, incapable of any strict classification. Here, as everywhere in the consideration of external forms, there are certain main types which present the strongest contrasts,—as the groups of the Arborescent Grasses, the Aloe form and the species of Cactus, Palms, Acicular-leaved trees, Mimosaceæ, and Bananas. Even scantily dispersed individuals belonging to these groups determine the character of a district, and produce a lasting impression on the mind of the unscientific but susceptible beholder. Other forms, perhaps more numerous and preponderating, may not appear equally marked either by the shape or position of the leaves; the relation of the stem to the branches, luxuriant vigour, animation, and grace; or even by the melancholy contraction of the leaf-organs.

As, therefore, a physiognomical classification, or a distribution into groups according to external appearance, does not admit of being applied to the whole vegetable kingdom collectively, the basis on which such a classification should be grounded must necessarily be wholly different from that which has been so happily chosen for the establishment of our comprehensive systems of the natural families of plants. Vegetable physiognomy grounds its divisions and the choice of its types on all that possesses mass,—as the stem, branches, and appendicular organs (the form, position, and size of the leaf, the character and brilliancy of the parenchyma), and consequently on all that is now included under the special term, the organs of vegetation, and on which depend the preservation (nourishment and development) of the individual; while systematic botany, on the other hand, bases the arrangement of the natural families of plants on a consideration of the organs of propagation, on which depends the preservation of the species.[^[RC]] It was already taught in the school of Aristotle,[^[RD]] that the generation of seed is the ultimate aim of the being and life of a plant. The process of development in the organs of fructification has become, since Caspar Fried. Wolf,[^[RE]] and our great poet Goëthe, the morphological basis of all systematic botany.

This science and that also of vegetable physiognomy proceed, I would here again observe, from two different points of view; the former depending upon an accordance in the inflorescence and in the reproduction of the delicate sexual organs; the latter on the conformation of the parts constituting the axes (the stem and branches) and on the outline of the leaves, which are mainly determined by the distribution of the vascular bundles. As, moreover, the stem and branches, together with their appendicular organs, predominate by mass and volume, they determine and strengthen the impression we receive, while they individualize the physiognomical character of the vegetation, as well as that of the landscape or the zone in which some distinguished types occur. The law is here expressed by the accordance and affinity in the marks appertaining to the vegetative, i.e. the nutritient organs. In all European colonies the inhabitants have been led by resemblances of physiognomy (habitus, facies) to apply the names of European forms to certain tropical plants, which bear wholly different flowers and fruits from the genera to which these designations originally referred. Everywhere in both hemispheres, the northern settler has believed he could recognise Alders, Poplars, Apple and Olive trees; being misled for the most part by the form of the leaves and the direction of the branches. The charm associated with the remembrance of native forms has strengthened the illusion, and European names of plants have thus been perpetuated from generation to generation in the slave colonies, where they have been further enriched by denominations borrowed from the negro languages.

A remarkable phenomenon is presented by the contrast frequently observed to arise from a striking accordance in physiognomy, coupled with the greatest difference in the organs of inflorescence and fructification—between the external form as determined by the appendicular or leaf-system, and the sexual organs on which are based the various groups of the natural systems of botany. One would be disposed à priori to believe that the aspect of vegetative organs (leaves) exclusively so called, must depend upon the structure of the organs of reproduction, but this dependence has only been observed in a very small number of families, as Ferns, Grasses, Cyperaceæ, Palms, Coniferæ, Umbelliferæ, and Aroideæ. In the Leguminosæ this accordance between the physiognomical character and the inflorescence can scarcely be recognized, excepting where they are separated into groups (as Papilionaceæ, Cæsalpinineæ, and Mimosaceæ.) The types which exhibit, when compared together, a very different structure of inflorescence and fructification, notwithstanding external accordance in physiognomy, are Palms and Cycadeæ, the latter being most nearly allied to the Coniferæ; Cucusta, belonging to the Convolvulaceæ, and the leafless Cassytha, a parasitical Laurinea; Equisetum (from the division of the Cryptogamia) and Ephedra (a coniferous tree). The Grossulareæ (Ribes) are so nearly allied by their efflorescence to Cactuses, i. e. the family of the Opuntiaceæ, that it is only very lately that they have been separated from them! One common family (that of the Asphodeleæ) comprises the gigantic tree, Dracœna Draco, the Common Asparagus, and the coloured flowering Aletris. Simple and compound leaves frequently belong not only to the same family, but even to the same genus. We found in the elevated plateaux of Peru and New Granada among twelve new species of Weinmannia, five with simple, and the remainder with pinnate leaves. The genus Aralia exhibits yet greater independence in the leaf-form, which is either simple, entire, lobed, digitate, or pinnate.[^[RF]]

Pinnate leaves appear to me to belong especially to those families which occupy the highest grade of organic development, as for instance, the Polypetalœ; among perigynic plants, the Leguminosæ, Rosaceæ, Terebinthaceæ, and Juglandeæ; among hypogynic plants the Aurantiaceæ, Cedrelaceæ, and Sapindaceæ. The elegant form of the doubly pinnate leaf, which constitutes so great an adornment of the torrid zone, is most frequently met with among the Leguminosæ; among the Mimosaceæ, and also among some Cæsalpinias, Coulterias and Gleditschias; but never, as Kunth has observed, among the Papilionaceæ.

The form of pinnate, and more especially of compound leaves, is unknown in Gentianeæ, Rubiaceæ, and Myrtaceæ. In the morphological development presented by the richness and varied aspect of the appendicular organs of dicotyledons, we are only able to recognize a very small number of general laws.

ON THE
STRUCTURE AND MODE OF ACTION
OF
VOLCANOS
IN DIFFERENT PARTS OF THE EARTH.

(This Memoir was read at a Public Meeting of the Academy, at Berlin, on the 24th January, 1823.)

When we consider the influence exerted on the study of nature during the last few centuries, by the extension of geographical knowledge and by means of scientific expeditions to remote regions of the earth, we are at once made sensible of the various character of this influence, according as the investigations have been directed to the forms of the organic world, the study of the inorganic crust of the earth, or to the knowledge of rocks, their relative ages, and their origin. Different vegetable and animal developments exist in every division of the earth, whether it be on the plains, where, on a level with the sea, the temperature varies with the latitude and with the various inflections of the isothermal lines, or on the steep declivity of mountain ranges, warmed by the direct rays of the sun. Organic nature imparts to every region of the globe its own characteristic physiognomy. But this does not apply to the inorganic crust of the earth divested of its vegetable covering, for everywhere, in both hemispheres, from the equator to the poles, the same rocks are found grouped with some relation to each other, either of attraction or repulsion. In distant lands, surrounded by strange forms of vegetation, and beneath a sky beaming with other stars than those to which his eye had been accustomed, the mariner often recognises, with joyful surprise, argillaceous schists and rocks familiar to him in his native land.

This independence of geological relations on the actual condition of climates does not diminish the beneficial influence exercised on the progress of mineralogy and physical geognosy by the numerous observations instituted in distant regions of the earth, but simply gives a particular direction to them. Every expedition enriches natural history with new genera of plants and animals. At one time we acquire a knowledge of new organic forms which are allied to types long familiar to us, and which not unfrequently, by furnishing links till then deficient, enable us to establish, in all its original perfection, an uninterrupted chain of natural structures. At another time we become acquainted with isolated structures, which appear either as the remains of extinct genera, or members of unknown groups, the discovery of which stimulates further research. It is not, however, from the investigation of the earth’s crust that we acquire these manifold additions to our knowledge, for here we meet rather with an uniformity in the constituent parts, in the superposition of dissimilar masses, and in their regular recurrence, which cannot fail to excite the surprise and admiration of the geologist. In the chain of the Andes, as in the mountains of Central Europe, one formation appears, as it were, to call forth another. Masses identical in character assume the same forms; basalt and dolerite compose twin mountains; dolomite, sandstone, and porphyry form abrupt rocky walls; while vitreous trachyte, containing a large proportion of feldspar, rises in bell-shaped and high-vaulted domes. In the most remote regions large crystals are separated in a similar manner from the compact texture of the fundamental mass, and, blending and grouping together into subordinate strata, frequently announce the commencement of new and independent formations. It is thus that the inorganic world may be said to reflect itself, more or less distinctly, in every mountain of any great extent. It is necessary, however, in order perfectly to understand the most important phenomena of the composition, relative age, and origin of formations, to compare together the observations made in regions of the earth most widely remote from each other. Problems which have long baffled the geologist in his own northern region, find their solution in the vicinity of the equator. If, as we have already observed, remote regions do not present us with new formations, that is to say, with unknown groupings of simple substances, they at least help us to unravel the great and universal laws of nature, by showing how different strata of the crust of the earth are mutually superimposed on, and intersect, each other in the form of veins, or rise to different elevations in obedience to elastic forces.

Although our geological knowledge may be thus extensively augmented by researches over vast regions, it can hardly be a matter of surprise that the class of phenomena constituting the principal subject of this address should have been so long examined in an imperfect manner, since the means of comparison were of difficult, and almost, it may be said, of laborious access.

Until towards the close of the eighteenth century all that was known of the form of volcanos and of the action of their subterranean forces was derived from observations made on two volcanic mountains of Southern Italy, Vesuvius and Etna. As the former of these was the more accessible, and (like all volcanos of slight elevation) had frequent eruptions, a hill became to a certain degree the type according to which a whole world—the mighty volcanos of Mexico, South America, and the Asiatic Islands—was supposed to be formed. Such a mode of reasoning involuntarily calls to mind Virgil’s shepherd, who believed that in his own humble cot he saw the image of the eternal city, Imperial Rome.

This imperfect mode of studying nature might indeed have been obviated by a more attentive examination of the whole Mediterranean, and especially of its eastern islands and littoral districts, where mankind first awoke to intellectual culture and to a higher standard of feeling. Among the Sporades, trachytic rocks have risen from the bottom of the sea, and have formed lands similar to those of the Azores, which in the course of three centuries have appeared periodically at three almost equal intervals of time. Between Epidaurus and Trœzene, near Methone, in the Peloponnesus, there is a Monte Nuovo, described by Strabo and since by Dodwell. Its elevation is greater than that of the Monte Nuovo of the Phlegræan fields near Baiæ, and perhaps even than that of the new volcano of Xorullo, in the plains of Mexico, which I found to be surrounded by many thousand small basaltic cones, upheaved from the earth, and still emitting smoke. It is not only in the basin of the Mediterranean, that volcanic fires escape from the permanent craters of isolated mountains having a constant communication with the interior of the earth, as Stromboli, Vesuvius, and Etna; for at Ischia, and on Mount Epomeus, and also, according to the accounts of the ancients, in the Lelantine plain, near Chalcis, lavas have flowed from fissures which have suddenly opened on the surface of the earth. Besides these phenomena, which fall within historical periods, that is, within the narrow bounds of authentic tradition, and which Ritter purposes collecting and explaining in his masterly work on geography, the shores of the Mediterranean present numerous remains of the earlier action of fire. The south of France exhibits in Auvergne a distinct and peculiar system of volcanos, linearly arranged, trachytic domes alternating with cones of eruption, emitting lava streams in the form of bands. The plains of Lombardy, which are on a level with the sea, and constitute the innermost bay of the Adriatic, inclose the trachyte of the Euganean Hills, where rise domes of granular trachyte, obsidian, and pearl-stone. These masses are developed from each other, and break through the lower chalk formations and nummulitic limestone, but have never been emitted in narrow streams. Similar evidence of former revolutions of our earth, is afforded in many parts of the Greek Continent and in Western Asia, countries which will undoubtedly some day yield the geologist ample materials for investigation, when the light of knowledge shall again shine on those lands whence it first dawned on our western world, and when oppressed humanity shall cease to groan beneath the weight of Turkish barbarism.

I allude to the geographical proximity of such numerous and various phenomena in order to show that the basin of the Mediterranean, with its series of islands, might have enabled the attentive observer to note all those phenomena which have recently been discovered under various forms and structures in South America, Teneriffe, and in the Aleutian islands, near the Polar region. The materials for observation were, no doubt, accumulated within a narrow compass; but it was yet necessary that travels in distant countries and comparisons between extensive tracts of land, both in and out of Europe, should be undertaken, in order to obtain a correct idea of the resemblance between volcanic phenomena and of their dependence on each other.

Language, which so frequently imparts permanence and authority to first, and often also erroneous views, but which points, as it were, instinctively to the truth, has applied the term volcanic to all eruptions of subterranean fire and molten matter; to columns of smoke and vapour which ascend sporadically from rocks, as at Colares, after the great earthquake of Lisbon; to Salses, or argillaceous cones emitting moist mud, asphalt, and hydrogen, as at Girgenti in Sicily, and at Turbaco in South America; to hot Geyser springs, which rise under the pressure of elastic vapours; and, in general, to all operations of impetuous natural forces which have their seat deep in the interior of our planet. In Central America (Guatimala) and in the Philippine Islands, the natives even formally distinguish between Volcanes de agua y de fuego, volcanos emitting water, and those emitting fire; designating by the former appellation, mountains from which subterranean waters burst forth from time to time, accompanied by a dull hollow sound and violent earthquakes.

Without denying the connection, which undoubtedly exists among the phenomena just referred to, it would seem advisable to apply more definite terms to the physical as well as to the mineralogical portion of the science of geology, and not at one time to designate by the word volcano a mountain terminating in a permanent fire-emitting mouth, and at another to apply it to any subterranean cause, be it what it may, of volcanic action. In the present condition of our earth, the form of isolated conical mountains (as those of Vesuvius, Etna, the Peak of Teneriffe, Tunguragua and Cotopaxi) is certainly the shape most commonly observed in volcanos. I have myself seen such volcanos varying in height from the most inconsiderable hill to an elevation of more than 19,000 feet above the level of the sea. Besides such conical forms, however, we continually meet with permanent fire-emitting mouths, in which the communication with the interior of the earth is maintained on far-extended jagged ridges, and not even always from the centre of their mural summits, but at their extremity towards their slope. Such, for instance, is Pichincha, situated between the Pacific and the city of Quito, which has acquired celebrity from Bouguer’s earliest barometric formulæ, and such are the volcanos on the Steppe de los Pastos, situate at more than 10,000 feet above the level of the sea. All these variously shaped summits consist of trachyte, formerly known as trap-porphyry; a granular stone full of narrow fissures, composed of different kinds of feldspar (labradorite, oligoklase, and albite), augite, hornblende, and sometimes interspersed mica, and even quartz. Wherever the evidences of the first eruption, the ancient structures—if I may use the expression—remain complete, the isolated cone is surrounded, circus-like, with a high wall of rock consisting of different superimposed strata, encompassing it like an outer sheath. Such walls or circular inclosures are termed craters of elevation, and constitute a great and important phenomenon, upon which that eminent geologist, Leopold von Buch, from whose writings I have borrowed many facts advanced in this treatise, presented so remarkable a paper to our Academy five years ago.

Volcanos which communicate with the atmosphere by means of fire-emitting mouths, such as conical basaltic hills, and dome-like craterless trachytic mountains, (the latter being sometimes low, like the Sarcouy, and sometimes high, like the Chimborazo,) form various groups. Comparative geography draws our attention, at one time, to small Archipelagos or independent mountain-systems, with craters and lava streams, like those in the Canary Isles and the Azores, and without craters or true lava streams, as in the Euganean hills, and the Siebengebirge near Bonn; at another time, it makes us acquainted with volcanos arranged in single or double chains, and extending for many hundred miles in length, either running parallel with the main direction of the range, as in Guatimala, Peru, and Java, or intersecting its axis at right angles, as in tropical Mexico. In this land of the Aztecs fire-emitting trachytic mountains alone attain the high snow limit: they are ranged in the direction of a parallel of latitude, and have probably been upheaved from a chasm extending over upwards of 420 miles, intersecting the whole continent from the Pacific to the Atlantic.

This crowding together of volcanos, either in rounded groups or double lines, affords the most convincing proof that their action does not depend on slight causes located near the surface, but that they are great and deep-seated phenomena. The whole of the eastern portion of the American continent, which is poor in metals, has in its present condition no fire-emitting openings, no trachytic masses, and perhaps no basalt containing olivine. All the volcanos of America are united in the portion of the continent opposite to Asia, along the chain of the Andes, which runs nearly due north and south over a distance of more than 7200 miles.

The whole elevated table-land of Quito, which is surmounted by the high mountains of Pichincha, Cotopaxi, and Tunguragua, constitutes one sole volcanic hearth. The subterranean fire bursts sometimes from one and sometimes from another of these openings, which have generally been regarded as independent volcanos. The progressive movement of the fire has, for three centuries, inclined from north to south. Even the earthquakes, which so fearfully devastate this portion of the globe, afford striking evidence of the existence of subterranean communications, not only between countries where there are no volcanos—as has long been known—but likewise between volcanic apertures situated at a distance from each other. Thus the volcano of Pasto, east of the river Guaytara, continued during three months of the year 1797, to emit, uninterruptedly, a lofty column of smoke, until it suddenly ceased at the moment of the great earthquake of Riobamba, (at a distance of 240 miles,) and the mud eruption of the “Moya,” in which from thirty to forty thousand Indians perished.

The sudden appearance, on the 30th of January, 1811, of the island of Sabrina, in the group of the Azores, was the precursor of the dreadful earthquakes which, further westward, shook, from May, 1811, to June, 1813, almost uninterruptedly, first the Antilles, then the plains of the Ohio and Mississippi, and lastly, the opposite coasts of Venezuela or Caracas. Thirty days after the total destruction of the beautiful capital of the province, there was an eruption of the long inactive volcano of St. Vincent, in the neighbouring islands of the Antilles. A remarkable phenomenon accompanied this eruption: at the moment of this explosion, which occurred on the 30th of April, 1811, a terrible subterranean noise was heard in South America, over a district of more than 35,000 square miles. The inhabitants of the banks of the Apure, at the confluence of the Rio Nula, and those living on the remote sea-coast of Venezuela, agreed in comparing this sound to the noise of heavy artillery. The distance from the confluence of the Rio Nula with the Apure (by which I entered the Orinoco) to the volcano of St. Vincent, measured in a straight line, is no less than 628 miles. This noise was certainly not propagated through the air, and must have arisen from some deep-seated subterranean cause; its intensity was, moreover, hardly greater on the shores of the Caribbean sea, near the seat of the raging volcano, than in the interior of the country in the basin of the Apure and the Orinoco.

It would be useless to multiply examples of this nature, by adducing others which I have collected: I will therefore only refer to one further instance, namely, the memorable earthquake of Lisbon, an important phenomenon in the annals of Europe. Simultaneously with this event, which took place on the 1st of November, 1755, not only were the Lakes of Switzerland and the sea off the Swedish coasts violently agitated, but in the eastern portion of the Antilles, near the islands of Martinique, Antigua, and Barbadoes, the tide, which never exceeds thirty inches, suddenly rose upwards of twenty feet. All these phenomena prove, that subterranean forces are manifested either dynamically, expansively, and attended by commotion, in earthquakes; or possess the property of producing, or of chemically modifying substances in volcanos; and they further show, that these forces are not seated near the surface in the thin crust of the earth, but deep in the interior of our planet, whence through fissures and unfilled veins they act simultaneously at widely distant points of the earth’s surface.

The more varied the structure of volcanos, that is to say, of elevations inclosing a channel through which the molten masses of the interior of the earth reach the surface, the more important it is to form a correct idea of these structures by careful measurement. The interest derived from measurements of this kind, which I made a special subject of inquiry in the western hemisphere, is increased by the consideration, that the objects to be measured vary in magnitude at different points. A philosophical study of nature seeks, in considering the changes of phenomena, to connect the present with the past.

In order to ascertain the periodic recurrence, or the laws of the progressive changes in nature, we require certain fixed points, and carefully conducted observations, which, by their connection with definite epochs, may serve as a basis for numerical comparisons. If the mean temperature of the atmosphere and of the earth in different latitudes, or the mean height of the barometer at the sea level, had been determined only once in every thousand years, we should know to what extent the heat of climates has increased or diminished, and whether any changes have taken place in the height of the atmosphere. Such points of comparison are especially required to determine the inclination and declination of the magnetic needle, and the intensity of those electro-magnetic forces on which Seebeck and Erman, two admirable physicists belonging to this Academy, have thrown so much light. If it be a meritorious undertaking on the part of learned societies to investigate with perseverance the cosmical changes in the heat and pressure of the atmosphere, and particularly the magnetic direction and intensity, it is no less the duty of the travelling geologist to direct attention to the varying height of volcanos in determining the inequalities of the earth’s surface. The observations which I formerly made in the Mexican mountains, at the volcano of Toluca, at Popocatepetl, at the Cofre de Perote, or Nauhcampatepetl, and Xorullo, and in the Andes of Quito at Pichincha, I have had opportunities since my return to Europe of repeating, at different periods, on Mount Vesuvius. Where complete trigonometric or barometric measurements are wanting, their place may be supplied by angles of altitude laid down with precision, and taken at points accurately determined. The comparison of such determinations, made at different periods of time, may sometimes be even preferable to the complication of more complete operations.

Saussure measured Vesuvius in 1773, and at that time both the north-western and south-eastern margins of the crater appeared to him to be equal in height. He found their elevation above the level of the sea to be 3894 feet. The eruption of 1794 occasioned a falling in towards the south, and an inequality in the margins of the crater, which may be distinguished from a considerable distance even by the most unpractised eye. Leopold von Buch, Gay Lussac, and myself, measured Mount Vesuvius three times in the year 1805, and found that the elevation of the northern margin, la Rocca del Palo, opposite the Somma, was exactly as it had been given by Saussure, while the southern margin was 479 feet lower than it had been in 1773. The elevation of the volcano itself towards Torre del Greco (the side towards which, for thirty years, the volcanic action has been principally directed) had, at that time, decreased one-eighth. The cone of cinders bears to the total height of Vesuvius the relation of 1 : 3; in Pichincha, the ratio is as 1 : 10, and at the Peak of Teneriffe, as 1 : 22. Of these three volcanic mountains, Vesuvius has, therefore, comparatively, the highest cone of cinders; probably because, being a volcano of inconsiderable height, it has chiefly acted through its summit.

A few months ago, in the year 1822, I succeeded not only in repeating my earlier barometric measurements of Mount Vesuvius, but also in determining more completely all the margins of the crater [^[108]] during three ascents of the mountain.

These determinations are, perhaps, deserving of some degree of attention, since they embrace the long period of the great eruptions between 1805 and 1822, and are probably the only measurements hitherto published of any volcano which admit of comparison in all their parts. They prove, that the margins of the crater should be regarded as a much more permanent phenomenon than has hitherto been supposed, from the hasty observations made on the subject; and that this character appertains to them everywhere, and not merely in those instances where, as at the Peak of Teneriffe, and in all the volcanos of the Andes, they evidently consist of trachyte. According to my latest determinations it would seem, that since the time of Saussure, a period of forty-nine years, the north-western margin of Vesuvius has probably not changed at all, and that the south-eastern one, in the direction of Bosche Tre Case, which in 1794 had become 426 feet lower, has since then only altered about 64 feet.

If, in the newspaper reports of great eruptions, we often find assertions made of an entire change of form in Mount Vesuvius, and if these assertions appear to be confirmed by the picturesque views of the volcano made at Naples, the cause of the error arises from the outlines of the margins of the crater having been confounded with those of the cones of eruption accidentally formed in its centre, the bottom of which has been raised by the force of vapours. A cone of eruption of this kind, formed by the accumulation of masses of rapilli and scoriæ, gradually came to view, above the south-eastern margin of the crater, between the years 1816 and 1818. The eruption in the month of February, 1822, increased this cone to such an elevation, that it projected from 107 to 117 feet above the north-western margin of the crater (the Rocca del Palo). This remarkable cone, which was at length regarded at Naples as the actual summit of Vesuvius, fell in with a fearful crash at the last eruption, on the night of the 22nd of October; in consequence of which, the bottom of the crater, which had continued uninterruptedly accessible from the year 1811, is now nearly 800 feet below the northern and 213 feet below the southern margin of the volcano. The varying form and relative position of the cones of eruption, the apertures of which must not, as they sometimes are, be confounded with the crater of the volcano, give to Vesuvius at different epochs a peculiar physiognomy; so much so, that the historiographer of this volcano, by a mere inspection of Hackert’s landscapes in the Palace of Portici, might guess the exact year in which the artist had made his sketch, by the outline of the summit of the mountain, according as the northern or southern side is represented in respect to height.

Twenty-four hours after the fall of the cone of scoriæ, which was 426 feet high, and when the small but numerous streams of lava had flowed off, on the night between the 23rd and 24th of October, there began a fiery eruption of ashes and rapilli, which continued uninterruptedly for twelve days, but was most violent during the first four days. During this period the explosions in the interior of the volcano were so loud that the mere vibrations of the air caused the ceilings to crack in the Palace of Portici, although no shocks of an earthquake were then or had previously been experienced. A remarkable phenomenon was observed in the neighbouring villages of Resina, Torre del Greco, Torre del’ Annunziata, and Bosche Tre Case. Here the atmosphere was so completely saturated with ashes that the whole region was enveloped in complete darkness during many hours in the middle of the day. The inhabitants were obliged to carry lanterns with them through the streets, as is often done in Quito during the eruptions of Pichincha. Never had the flight of the inhabitants been more general, for lava streams are less dreaded even than an eruption of ashes, a phenomenon unknown here in any degree of intensity, and one which fills the imaginations of men with images of terror from the vague tradition of the manner in which Herculaneum, Pompeii, and Stabiæ were destroyed.

The hot aqueous vapour which issued from the crater during the eruption, and diffused itself through the atmosphere, formed, on cooling, a dense cloud, which enveloped the column of ashes and fire, that rose to an elevation of between 9000 and 10,000 feet above the level of the sea. So sudden a condensation of vapour, and, as Gay Lussac has shown, the formation of the cloud itself, tended to increase electric tension. Flashes of forked lightning darted in all directions from the column of ashes, while the rolling thunder might be clearly distinguished from the deep rumbling sounds within the volcano. In no other eruption had the play of the electric forces been so powerfully manifested as on this occasion.

On the morning of the 26th of October the strange report was circulated that a stream of boiling water was gushing from the crater, and pouring down the cone of cinders. Monticelli, the zealous and learned observer of the volcano, soon perceived that this erroneous report originated in an optical illusion, and that the supposed stream of water was a great quantity of dry ashes which issued like drift sand from a crevice in the highest margin of the crater. The long drought, which had parched and desolated the fields before this eruption of Vesuvius, was succeeded, towards the termination of the phenomenon, by a continued and violent rain, occasioned by the volcanic storm which we have just described. A similar phenomenon characterizes the termination of an eruption in all zones of the earth. As the cone of cinders is usually wrapped in clouds at this period, and as the rain is poured forth with most violence near this portion of the volcano, streams of mud are generally observed to descend from the sides in all directions. The terrified peasant looks upon them as streams of water that rise from the interior of the volcano and overflow the crater, while the deceived geologist believes that he can recognise in them either sea-water or muddy products of the volcano, the so-called eruptions boueuses, or, in the language of the old French systematisers, products of an igneo-aqueous liquefaction.

Where, as is generally the case in the chain of the Andes, the summit of the volcano penetrates beyond the snow-line, attaining sometimes an elevation twice as great as that of Mount Etna, the inundations we have described are rendered very frequent and destructive, owing to the melting and permeating snow.

These are phenomena which have a meteorological connection with the eruptions of volcanos, and are variously modified by the heights of the mountains, the circumference of the summits which are perpetually covered with snow, and the degree to which the walls of cinder cones become heated; but they cannot be regarded in the light of true volcanic phenomena. Subterranean lakes, communicating by various channels with the mountain streams, are frequently formed in deep and vast cavities, either on the declivity or at the base of volcanos. When the whole mass of the volcano is powerfully shaken by those earthquakes which precede all eruptions of fire in the Andes, the subterranean vaults open, and pour forth streams of water, fishes, and tuffaceous mud. This singular phenomenon brings to mind the Pimelodes Cyclopum, or the Silures of the Cyclops, which the inhabitants of the plateau of Quito call Preñadilla, and of which I gave a circumstantial account soon after my return to Europe. When, on the night between the 19th and 20th of June, 1698, the summit of Mount Carguairazo, situated to the north of Chimborazo, and having an elevation of more than 19,000 feet, fell in, all the country for nearly 32 square miles was covered with mud and fishes. A similar eruption of fish from the volcano of Imbaburu was supposed to have caused the putrid fever, which, seven years before this period, raged in the town of Ibarra.

I refer to these facts because they throw some light on the difference between the eruption of dry ashes and mud-like inundations of tuff and trass, investing fragments of wood, charcoal, and shells. The quantity of ashes recently erupted from Mount Vesuvius, like every phenomenon connected with volcanos and other great and fearful natural phenomena, has been greatly exaggerated in the public papers; and two Neapolitan chemists, Vicenzo Pepe and Guiseppe di Nobili, even asserted that the cinders were mixed with given proportions of gold and silver, notwithstanding the counter-statements of Monticelli and Covelli. According to my researches the stratum of ashes which fell during the twelve days was only three feet in thickness in the direction of Bosche Tre Case, on the declivity of the cone, where they were mixed with rapilli, while in the plains its greatest thickness did not exceed from 16 to 19 inches. Measurements of this kind must not be made at spots where the ashes have been drifted by the wind, like snow or sand, or where they have been accumulated in pulp-like heaps by means of water. The times are passed in which, after the manner of the ancients, nothing was regarded in volcanic phenomena save the marvellous, and when men would believe, like Ctesias, that the ashes from Etna were borne as far as the Indian peninsula. A portion of the Mexican gold and silver veins is certainly found in trachytic porphyry, but in the ashes of Vesuvius which I myself collected, and which were, at my request, examined by that distinguished chemist Heinrich Rose, no trace of either gold or silver was to be discovered.

However much these results, which perfectly correspond with the more exact observations of Monticelli, may differ from those recently announced, it cannot be denied that the eruption of ashes, which continued from the 24th to the 28th of October, is the most memorable that has been recorded, on unquestionable evidence, in reference to Mount Vesuvius, since the death of the elder Pliny. The quantity of ashes erupted on this occasion was probably three times as great as the whole quantity which has fallen since volcanic phenomena have been observed with attention in Italy. A stratum from 16 to 19 inches in thickness does certainly, at first sight, seem very inconsiderable, when compared with the mass with which we find Pompeii covered. But, without taking into account the heavy rains and the inundations which must have increased the bulk of this stratum in the course of ages, and without reviving the animated contention maintained with much scepticism on the other side of the Alps, regarding the causes of the destruction of the Campanian cities, it may, at any rate, be here observed that the eruptions of a volcano, at widely remote epochs, cannot be compared with respect to their intensity. All conclusions must be insufficient that are based on mere analogies of quantitative relations of the lava and ashes, the height of the column of smoke, and the intensity of the explosions.

We learn from the geographical description of Strabo, and from the opinion expressed by Vitruvius on the volcanic origin of pumice, that, until the year of Vespasian’s death, that is to say, until the eruption which buried Pompeii, Vesuvius appeared more like an extinct volcano than a Solfatara. When, after a long-continued repose, subterranean forces suddenly opened for themselves new channels, penetrating through strata of primitive rock and trachyte, effects must have been produced to which no analogy is afforded by those of subsequent occurrence. We clearly learn from the well-known letter in which Pliny the younger informs Tacitus of the death of his uncle, that the renewal of the eruptions, or, one might almost say, the revival of the slumbering volcano, began with an outbreak of ashes. The same phenomenon was observed at Xorullo, when the new volcano, in the month of September, 1759, breaking through strata of syenite and trachyte, was suddenly upheaved in the plain. The country people fled in terror on finding their cottages covered with ashes thrown up from the earth, which was bursting in every direction. In the ordinary periodical manifestations of volcanic activity a shower of ashes usually terminates each partial eruption. The letter of the younger Pliny contains, moreover, a passage which clearly shows that the dry ashes falling from the air immediately attained a height of four or five feet, independent of accumulation by drifts. “The court,” the narrative continues, “which led to the apartment in which Pliny took his siesta, was so filled with ashes and pumice that, had the sleeper tarried longer, he would have found the passage wholly blocked up.” Within the inclosed limits of a court the wind cannot have exercised any very considerable influence on the drifting of the ashes.

I have interrupted my comparative view of volcanos by different observations in relation to Vesuvius, partly on account of the great interest excited by its recent eruption, and partly because every great outpouring of ashes almost involuntarily recalls to mind the classic soil of Pompeii and Herculaneum. In a note, not adapted to be read to the audience to whom this lecture is addressed, I have collected all the elements of the barometric measurements which I made during the close of last year at Mount Vesuvius, and in the Campi Phlegræi.

We have hitherto considered the form and effects of those volcanos which are permanently connected, by means of a crater, with the interior of the earth. The summits of such volcanos are upheaved masses of trachyte and lava intersected by numerous veins. The permanency of their effects indicates a highly complex structure. They have, so to say, a certain individuality of character, which remains unaltered for long periods of time. Contiguous mountains generally yield wholly different products; for instance: leucitic and feldspathic lavas, obsidian with pumice, and basaltic masses containing olivine. They belong to the more recent phenomena of the earth, usually breaking through all the strata of the floetz formation, and their lava currents and products are of subsequent origin to our valleys. Their life, if I may be permitted to use a figurative expression, depends upon the mode and the duration of their connection with the interior of the earth. After continuing for centuries in a state of repose, their activity is often suddenly revived, and they then become converted into Solfataras, emitting aqueous vapours, gases, and acids. Occasionally, as at the Peak of Teneriffe, their summits have already become a laboratory of regenerated sulphur, while considerable lava currents, being basaltic near the base, and mixed with obsidian and pumice at greater elevations, where the pressure is less, continue to flow from the sides of the mountain [^[109]].

Besides volcanos which have permanent craters, there is another kind of volcanic phenomena less frequently observed than the former, but especially instructive to the geologist, as they remind us of the primitive world, that is, of the earliest revolutions of our planet. Trachytic mountains suddenly open, and after throwing up ashes and lava, close again never perhaps to re-open. Such has been the case with the mighty volcano of Antisana in the chain of the Andes, and with Mount Epomæus in Ischia, in the year 1302. Occasionally such an eruption has occurred even in the plains, as on the table-land of Quito, in Iceland at a distance from Hecla, and in the Lelantine plains of Eubœa. Many upheaved islands belong to this class of transitory phenomena. In these cases, the connection with the interior of the earth is not permanent, the action ceasing as soon as the fissure, or channel of communication, is again closed. Veins of basalt, dolerite, and porphyry, which traverse almost all formations in different parts of the earth; and the masses of syenite, augitic porphyry, and amygdaloid, which characterise the most recent strata of transition rock, and the oldest stratum of the floetz formation; have all probably been formed in a similar manner. In the youthful period of our planet, the substances that had continued in a fluid condition within the earth, broke through its crust, everywhere intersected with fissures, and became solidified as granular veins, or were spread out in broad superimposed strata. The products that may be termed exclusively volcanic, which have come down to us from the primitive ages of the world, have not flowed in streams or bands like the lava of our isolated conical mountains. The mixtures of augite, titanic iron, feldspar, and hornblende, may have been the same at different periods, sometimes allied to basalt, sometimes to trachyte; while chemical substances, (as we learn from Mitscherlich’s important labours and the analogies presented by artificial igneous products,) may have ranged themselves in layers according to some definite laws of crystallization. In all cases we perceive that substances similarly composed have come to the surface of the earth by very different means, either by being simply upheaved, or escaping through temporary fissures; and that breaking through the older rocks, that is to say, through the earlier oxidized earth’s crust, they have flowed in the form of lava streams from conical mountains having a permanent crater. If we do not sufficiently distinguish between these various phenomena, our knowledge of the geology of volcanos will again be shrouded in that obscurity, from which numerous comparative experiments are now beginning gradually to release it.

The questions have often been asked, what is it that burns in volcanos, what generates the degree of heat capable of mixing earths and metals together in a state of fusion? Modern chemistry has attempted to reply that it is the earths, metals, and alkalies themselves, that is to say, the metalloids of these substances, which burn. The solid and already oxidized crust of the earth separates the surrounding atmosphere, with the oxygen it contains, from the combustible unoxidized substances in the interior of our planet. By the contact of these metalloids with the atmospheric oxygen the disengagement of caloric ensues. The celebrated and talented chemist, who advanced this explanation of volcanic phenomena, soon himself relinquished it. The experiments which have been made in mines and caverns in all parts of the earth, and which M. Arago and myself have collected in a separate treatise, prove that even at an inconsiderable depth, the temperature of the earth is much higher than the mean temperature of the atmosphere at the same place. This remarkable, and almost universally confirmed fact, is connected with what we learn from volcanic phenomena. The depth at which we might regard the earth as a fused mass, has been calculated. The primitive cause of this subterranean heat is, as in all planets, the formative process itself, the separation of the spherically conglomerating mass from a cosmical aëriform fluid, and the cooling of the terrestrial strata at different depths by the radiation of heat. All volcanic phenomena are probably the result of a permanent or transient connection between the interior and the exterior of our planet. Elastic vapours press the fused oxidizing substances upwards through deep fissures. Volcanos therefore are intermittent earth-springs, from which the fluid mixtures of metals, alkalies, and earths, which become consolidated into lava currents, flow gently and calmly, when being upheaved they find a vent. In a similar manner, according to Plato’s Phædon, the ancients regarded all volcanic streams of fire as effusions of the Pyriphlegethon.

I would fain be permitted to add one yet bolder observation to those I have already ventured to advance. May not the cause of one of the most wonderful phenomena presented by the study of petrifactions, be dependent on the condition of the inner heat of our planet, which is indicated by thermometric experiments on springs [^[110]] rising from different depths, and by observations on volcanos? We find tropical animals, arborescent ferns, palms, and bamboos, buried in the cold north, and everywhere the primitive world presents a distribution of organic structures wholly at variance with existing climatic relations. Many hypotheses have been advanced in elucidation of so important a problem, such as the approximation of a comet, the altered obliquity of the ecliptic, and the increased intensity of the sun’s light; but none of these have satisfied at once the astronomer, the physicist, and the geologist. I, for my part, would willingly leave undisturbed the axis of the earth or the light of the sun’s disk, (from whose spots a celebrated astronomer explained fruitfulness and failure of crops,) yet it appears to me that in every planet there exist, independently of its relations to a central body and its astronomical position, numerous causes for the development of heat, in processes of oxidation, in precipitation, in the chemically altered capacity of bodies, the increase of electro-magnetic tension, and in the channels of communication opened between its internal and external parts.

Wherever, in the primitive world, heat was radiated from the deeply fissured crust of the earth, palms, arborescent ferns, and all the animals of the torrid zone, could perhaps have flourished for centuries over extensive tracts of land. According to this view, which I have already published in my work entitled Geognostischer Versuch über die Lagerung der Gebirgsarten in beiden Hemisphären,[^[RG]] the temperature of volcanos would be that of the interior of our earth itself, and the same causes which now occasion such fearfully devastating results, may have been able to produce, in every zone, the most luxuriant vegetation on the newly oxidized crust of the earth and on the deeply fissured strata of rocks.

Should it be assumed, for the purpose of explaining the wonderful distribution of tropical forms in their ancient mausolea, that the long-haired elephantine animals, which are now found embedded in ice, were once indigenous to northern latitudes, and that animals of similar forms, belonging to the same type, as, for instance, lions and lynxes, were capable of living in wholly different climates, such a mode of explanation would at all events not admit of being extended to vegetable products. From causes developed by the physiology of vegetation, palms, bananas, and arborescent monocotyledons, are unable to endure the deprivation of their appendicular organs, by the northern cold; and in the geological problem which we are here considering, it seems to me a matter of difficulty to admit any distinction between vegetable and animal structures. One and the same mode of explanation must be applied to both forms.

In concluding this treatise, I have added some uncertain and hypothetical conjectures to the facts which have been collected in widely remote regions of the earth. The philosophical study of nature rises above the requirements of mere delineation, and does not consist in the sterile accumulation of isolated facts. The active and inquiring spirit of man may therefore be occasionally permitted to escape from the present into the domain of the past, to conjecture that which cannot yet be clearly determined, and thus to revel amid the ancient and ever-recurring myths of geology.

ILLUSTRATIONS AND ADDITIONS.

ON THESTRUCTURE AND MODE OF ACTIONOFVOLCANOSIN DIFFERENT PARTS OF THE EARTH.

ON THE
STRUCTURE AND MODE OF ACTION
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VOLCANOS
IN DIFFERENT PARTS OF THE EARTH.