FOOTNOTES:
[12] This question is specially considered in Descartes' "Discours sur la Méthode."
[13] "De l'Instinct et de l'Intelligence des Animaux," Paris, 1861.
[14] "Etudes Philosophiques sur l'Instinct et l'Intelligence des Animaux," Strasbourg, 1853.
CHAPTER THE TWELFTH.
WHAT IS THE PLANT?—THE PLANT IS SENSIBLE.—HOW DIFFICULT IT IS TO DISTINGUISH PLANTS FROM ANIMALS.—THE GENERAL CHAIN OF LIVING BEINGS.
LINNÆUS has said, "The plant lives; the animal lives and feels; man lives, feels, and thinks." This aphorism represented the state of science in the times of Linnæus. But since the year 1778, that is to say, since the death of the great botanist, Upsal, natural science has progressed, botany and zoology have been enriched with innumerable facts and fundamental discoveries, so that the Linnæan formula no longer represents the present condition of the sciences of organization. We believe that the following proposition may be truthfully substituted: "The plant lives and feels; the animal and man live, feel, and think."
To accord sensibility to plants, is to transgress the classic laws of natural history, so that the considerations and facts which appear to us to justify this proposition ought to be most carefully stated.
1. The plant feels the sensations of pleasure and pain. Cold, for instance, impresses it painfully; it may be seen to contract itself, as if shivering, under the influence of a sudden or excessive fall of the temperature. An abnormal excess of temperature evidently causes it to suffer; when the heat is very great, leaves may be observed to hang down on the stems, curl up, and appear to wither; when the cool of the evening comes, the leaves rise up again, and the plant resumes its appearance of placid health. Drought also occasions manifest suffering to plants. Those who study nature with loving attention know that when, after a long period of drought, a plant is watered it exhibits signs of pleasure. On the other hand, a wounded plant, one from which a branch has been cut, appears to experience pain. A pathological liquid exudes from the wound, like the blood from a hurt animal; the plant is sick, and will die, if it do not receive the necessary succour. Thus persons who love plants will not cut flowers off their stems, they prefer to inhale their perfume, and contemplate their brilliant colours, on the stalk, without inflicting a painful mutilation upon the beautiful creatures which they admire.
The sensitive plant, if touched by the fingers, or even struck by a current of harsh air, folds up its leaves, and contracts itself. The botanist, Desfontaines, saw a sensitive plant, which he was bringing home in a carriage, contract its leaves while the vehicle was in motion, and expand them when it stopped, thus affording a proof that the movement distressed the plant. A drop of acid, or acrid liquid, placed on a leaf of a sensitive plant, will occasion a similar constriction. All vegetables present an analogous phenomenon. Their tissues contract when brought in contact with irritant substances. By rubbing the tips of a lettuce, the juice may be made to exude.
Vegetable sensibility exists by the same right as animal sensibility, since electricity kills plants as it kills animals, since narcotic poisons kill or stupefy plants as they kill and stupefy animals. One can narcotize a plant by watering it with opium dissolved in water, and MM. Gopport and Macaire have discovered that hydrocyanic acid kills plants as rapidly as animals.
2. Plants sleep at night. During the day they develop their vital activity, and when the night comes, or when they are in darkness, their leaves assume another position, that of repose; they fold themselves up. In the day-time, the upper surface of the leaf is turned to the sky, and the under surface towards the earth; this under surface, pierced with holes, or stomata, is the part through which absorption and exhalation take place, while the upper surface, in which there are no such openings, is only a sort of screen for the protection of the absorbing surface. It is therefore easy to understand that the horizontal attitude of the leaves is a position of vital activity, and that the refolding of those leaves during the night indicates a state of repose. It is precisely the same case with ourselves, when during the night we indulge our muscles, kept on the stretch during the day, with complete relaxation.
The sleep of plants, said to have been discovered by Linnæus, and which was certainly described for the first time in one of Upsal's Thèses de Botanique, and thoroughly elucidated by Linnæus, is not a phenomenon limited to certain families of plants. There are very few vegetables which, during the night, or in darkness, do not fold their leaves, and which do not present a different appearance by day and by night. The Sensitive is the classic plant selected for its exhibition of this phenomenon in all its intensity; but this small leguminous creature only presents us with an exaggeration of a fact which exists in a lesser degree among almost all vegetables with light leaves. We may quote the following passage from a former work on the subject of this phenomenon.
"The sleep of plants vaguely resembles that of animals. It is a remarkable circumstance that the slumbering leaf appears to wish to return to the epoch of its infancy. It folds itself almost as it was when in the bud, before it burst out, as it was in the lethargic sleep of winter, sheltered beneath its strong scales, or wrapped up in its warm down. One would think that the plant was trying every night to resume the position which it occupied in its early time, just as the sleeping animal gathers himself together, and folds his limbs as they were folded in his mother's womb."[15]
Is it possible to deny the possession of sensibility to creatures which give us alternate sign of repose and of activity, and who have the power of accommodating themselves to various external impressions? Fatigue cannot possibly be anything but the consequence of the experience of an impression.
3. Numerous physiological functions are fulfilled by plants as well as by animals; and when we consider the number and variety of these functions, it is difficult to understand how, if animals be, as the common consent of mankind declares them, possessed of sensibility, plants can be destitute of it. An ancient philosopher defined plants as animals with roots. We shall see, on examining the variety of functions performed by vegetables, whether this philosopher was not a far-seeing, wise man.
It would be difficult to name any function with which the animal is invested that the vegetable does not possess in a less degree. Respiration, for instance, is equally a property of plants and of animals. Among the latter, respiration consists in the absorption of the oxygen of the air and the emission of carbonic acid gas and watery vapour; among plants it consists in the emission of carbonic acid gas and watery vapour during the night, and during the day, under the influence of sunlight, of the emission of oxygen proceeding from the decomposition of carbonic acid. The function is evidently of the same nature in both the natural kingdoms.
Exhalation is a function common to vegetables and to animals. By the stomata of leaves, as by the pores of the skin of animals, watery vapour and various gases, according to the vital phenomena which take place in the interior of the tissues, are constantly being disengaged.
Absorption takes place in both kingdoms. If you pour water on the lower surface of a leaf, you will see that it will be absorbed with great rapidity. Sprinkle a bouquet of flowers with water, and the freshness of the withered blossoms will revive. Absorption is even more active in vegetable than in animal tissues.
The circulation of liquids in the interior of plants is accomplished by a complicated system of channels and vessels of every order and of every calibre, absorbent vessels, exhalant vessels.
Nothing is more varied than the disposition of these channels in the interior of plants, and their multiplicity indicates a circulatory function as complicated as that of animals.
It is then evident that vegetables have the same physiological functions as animals, but as yet we know those functions very imperfectly. It is very strange that while animal physiology is so far advanced in our day, vegetable physiology is almost in its infancy. We know very well how the digestion of food takes place in man and animals, we know how our blood circulates in a double system of vessels, called arteries and veins, and we know the central organ, the heart, through which the two liquids are carried by this double system. We see and we touch the organs of sensation and motion, that is to say, the nerves. More than this, we distinguish the nerves which produce sensation from those which rule motion. We know that the centre of nervous action in man and animals is double; that its seat is equally in the brain and in the spinal marrow.
Briefly, science has shed its brightest light on all the functions belonging to animal organization, while vegetable physiology remains in obscurity. Notwithstanding the labours of naturalists within the last two centuries, we cannot explain the life of plants with certainty. We cannot positively state how the sap, which is vegetable blood, circulates in their channels. We do not even know with precision whether a tree grows from the outside to the inside, or from the inside to the outside. All the physiological functions in the vegetable kingdom are hidden from us by a thick veil, and it is only by lifting a corner of it with great difficulty that we can catch a few gleams of light through the obscurity. Nevertheless, all unexplained though they be as yet, physiological functions do exist in plants. Considering these numerous functions, it appears entirely impossible that plants should not have received the gift of sensibility. It is difficult to believe, as Linnæus would have us believe, that they possess life, and nothing more.
We shall be told that vegetables have no nerves, and that in the absence of every organ of sensation, we cannot accord them the faculty of sensibility. But, we reply, that the imperfect state of vegetable anatomy and physiology forbids us to come to any conclusion touching the existence or the absence of nerves in plants. We are convinced that these organs exist, but that botanists do not know how to discern them, or have no means of distinguishing between them and other organs.
4. The manner of multiplication and reproduction among plants and animals is so analogous, that it seems impossible, when we consider this extraordinary resemblance in the most important functions, to refuse sensibility to plants, and accord it to animals.
Let us consider the various modes of reproduction proper to vegetables. Reproduction, or rather the fecundation which precedes it, is executed in certain vegetables, by means of an apparatus of the same typical form as that of the animal kingdom. It is composed of a male organ, the stamen, which contains the impregnating dust, pollen, and of a female organ, the ovary, supported by a stalk, the pistil. The pollen impregnates the ovula contained in the grains of pollen in the ovary, as the seed of the male impregnates the ovula contained in the egg of the animal. In both cases the fruit of the impregnation develops itself afterwards with the aid of warmth and time. The vegetable egg grows and ripens, just as the animal egg grows and ripens.
We may add that the analogy between the modes of reproduction, in the two kingdoms, animal and vegetable, does not limit itself to these conditions of likeness; we may observe resemblances in the specialities of the function. Particular vitality, a turgid state of the tissues, accompanied by elevation of the local temperature, occur in the case of certain plants at the moment of impregnation, especially in the species of the family of Aroïdes. On placing a thermometer, at that time, in the great floral covering of the Arums, an excess of from 1° to 2° on the temperature of the surrounding air will be denoted, an extraordinary fact in vegetable life, for vegetables are always colder than the external air. How can we believe that the plant in which this excitement takes place has no feeling of its own condition? The plant, like the animal, has its seasons of love, can it be that it has no consciousness of them? Are we to believe that the plant which becomes warm, in which life rises at the moment of impregnation, has no more sensation than a stone? Such is not our opinion. We cannot understand life without sensibility—the one appears to us to be the indication of the other.
The analogy between the plant and the animal in their functions of reproduction is nowhere more evident or more curious than in a vegetable production which abounds in the waters of the Rhône, and has received the name of Vallisneria spiralis. In this plant the male and female organs are placed on different branches of the same plant. The female flowers are fixed to the ground by long, twisted, spiral stalks. But, when seeding time comes, the spirals of the stems unroll themselves, and the female flowers come up to the surface of the water and spread themselves out. The male flowers, not being placed like the female on elastic stems, cannot come up to the surface of the water. What do they do? They burst through their covering, and float around their females on the surface of the water. After that the current carries away the detached male flowers; and the female stem folds itself up again, and sinks to the bottom of the river, there to ripen its impregnated ovules.
The function of reproduction in plants is rich in conclusions in support of our thesis. The plants called phanerogamous are not reproduced only by impregnation by means of the visible sexual organs, the pistil and the stamen, they are also multiplied by grafts, buds, and cuttings. Cryptogamous plants, which have no sexual organs, are multiplied either by effects which detach themselves from the individual plant at a certain period of its vegetation as we see in the case of fungi, algæ, mushrooms, &c., or by fragments of the individual itself, which, being thrown into the ground, germinate and multiply themselves.
Animals, in their several classes, represent all these modes of reproduction; there is not one which does not exist among them. Animals are not reproduced by eggs only, either interior or exterior, and by living young ones, they are equally multiplied, like vegetables, by offsets, by cuttings, and by ingraftment.
Multiplication by offsets may be observed in the fresh-water polype. Little buds which grow and lengthen come out of the body of this animal. While the bud is lengthening, he throws off other and smaller offsets, which throw off still smaller ones. All these are so many little polypes, which derive their nourishment from the principal polype. Having attained a certain size, these offsets separate themselves from the primitive individual, and constitute so many new polypes. Coral multiplies itself in the same manner. From the principal branch spring secondary branches which have originated in a bud or shoot, and these branches, inserting themselves into the chief stem, form new individuals. Thus the exterior aspect of the coral resembles a ramified tree rather than an animal.
Madrepores, another kind of zoophytes, resemble trees so closely, that for centuries they were supposed to be marine plants; they too, like coral, are reproduced by offsets.
Multiplication by cuttings is seen in the fresh-water polype. Take a fresh-water polype, and cut it into as many fragments as you choose. Each of these fragments, left to itself, will become a polype. These new individuals may be in their turn cut into pieces, which will produce as many new ones. This is multiplication by cuttings, exactly similar to the process in plants, so that the generation of fresh-water polypes does not differ from that of one of our fruit-trees. It is not only the entire polype which, thus cut to fragments, furnishes a new polype; the skin of this animal can also produce one new individual or several. Is not this a vegetable ingraftment?
A similar generation by ingraftment is to be observed in another instance, in the case of the fresh-water polype. Take different portions of the same polype, or those of different polypes, and join them at the ends, or lay them upon one another, and you will combine them so closely that they reciprocally nourish each other, and ultimately form only one individual. Here is vegetable ingraftment carried out in an animal.
5. Other points of resemblance exist between plants and animals. If they are not generally remarked, it is because the authors of the classics of natural history do not direct the attention of the reader to these facts. We are about to supplement their silence, and to bring the analogies between the two natural kingdoms into view.
Firstly, there exists in both a common and equally astonishing fecundity. Among plants, as among animals, one individual can give birth to thousands of individuals like himself. Vegetables are even more fertile than the superior animals. Trees produce every year, and sometimes for a century. Mammiferous animals, birds, and reptiles produce infinitely less than trees; their pregnancy is less frequent, and takes place during a certain period in the life of the animal only. The elm produces every year more than 300,000 seeds, and this may continue for a hundred years. Fish and insects approach most nearly to trees in fecundity. A tench spawns 10,000 eggs yearly, a carp 20,000. Among insects, a female bee produces from 40,000 to 50,000 eggs. To these animals we may compare, among vegetables, the poppy, the fern, the mustard plant, which produce incalculable quantities of seeds. We must not forget, besides, that vegetables multiply themselves in many ways, whereas each animal possesses but one mode of reproduction.
What we wish to establish, what is evident, is that among both animals and plants fecundity is equal, and equally prodigious. From the point of view of this analogy, we may also quote the size of the species, which is extremely variable in both kingdoms, because both produce at the same time giant species and dwarf species. Among animals, there are some of monstrous size, such as the whale, the cachalot, and the elephant, such as the gigantic reptiles of the ancient world, the ichthyosaurus, which was longer than the whale, the megalosaurus and the iguanadon, which were as large as the elephant.
To these colossi of the animal kingdom, we may oppose the colossi of the vegetable kingdom; the monstrous baobab gourd, which covers hundreds of square yards with its shade, the elm, whose trunk may grow to the size of a whale's girth, the Eucalyptus globulus, an Australian tree which is being acclimatized in Algeria and in the south of France, the Sequioœa gigantea, the giant of Californian forests.
If the two kingdoms of nature have their colossi, they have also their dwarfs, and their infinitely little. There are cryptogamic vegetables which are only to be seen with the microscope, and there are animalculæ equally invisible to the naked eye. If the animal kingdom can show, in its scale of size, the whale, and the microscopic acarus, the vegetable kingdom possesses a similar decreasing scale from the baobab to the lichens.
The same places are inhabited or resorted to by plants and animals. Both live on the same soil, as if for mutual aid. The two kingdoms combine at all points of the globe. We might name a number of places in which certain plants and certain animals thrive together. The chamois and the maple tree love the same mountains, the same high places; the truffle and the earth-worm dwell in the same underground region; the birch and the hare are found in the same place; the water-lily grows in the same fresh water with the aquatic worm; and the cod and the algæ prosper in the same submarine depths.
All vegetables and animals have an original country, but they can be acclimatized under other skies by human industry and skill. The chestnut-tree and the Indian cock, the peach-tree and the turkey, transported to Europe, has each forgotten its native land.
Among both animals and plants there are amphibious creatures. The frog, and the other batrachians, live, like the reeds, on the earth and in the water. Both animals and plants can live as parasites. The animal world has the flea, the louse, the acarus; the vegetable world has its lichens, and its mushrooms.
Thus, equal fecundity, similar variety in the scale of size, analogy in habitation, which implies ideality of organization, possibility of transplantation and of acclimatization out of their original country, possibility of amphibious existence, parasitical life, all general conditions which suppose a great analogy of organization; we establish all these things in drawing the parallel between plants and animals. How, then, if we grant sensibility to one of these kingdoms, can we deny it to the other?
6. Plants, like animals, have their maladies. We do not now allude to maladies caused by parasites, like the sickness of the vine, due to the oïdium Tuckeri, the sickness of the petals, caused by other small mushrooms, that of the rose-tree, the olive-tree, of corn, &c., produced by parasitical cryptogams, which fix themselves on the plant, and change the normal course of its life; we speak of morbid affections, properly so called. The pathological condition and its consequences exist in the plant as in the animal. Stoppage, or febrile and abnormal acceleration of the sap in the vegetable, answer to stagnation of the blood, or its acceleration during fever, in the animal; various excrescences of the bark, analogous to affections of the skin; the abortion of certain organs, and the capricious development of others; the secretion of pathological liquids which flow outside. This is a brief catalogue of the maladies to which trees, shrubs, and herbaceous vegetables are subject. A plant which passes too quickly and too often from intense cold to extreme heat, soon becomes ill, and necessarily perishes, like an animal exposed to those dangerous alterations. A shrub left in a current of cold air could no more live than an animal if kept in a similar place. In a word, the plant exhibits health or sickness, according to its conditions of existence. How can we admit that the being in which such changes take place, can be merely the passive subject of them, that it experiences neither pain nor pleasure in passing from health to sickness, or from sickness to health?
7. Sicknesses, or other causes, produce anomalies of form, or irregularities of structure in plants, as in animals. Just as in the animal kingdom monstrosities exist, there are monstrosities in the vegetable kingdom. The science which occupies itself with monstrosities in animals is called teratology. Geoffrey St. Hilaire has made some most interesting studies of the causes of the productions of monsters in the different classes of animals; but it has been perceived of late that an analogous science must be created, for the explanation of monstrosities proper to the vegetable kingdom, and Moquin Tandon has published a book upon vegetable teratology.
8. Old age and death are common to both plants and animals. Plants, after having survived the various maladies which threaten them, do not escape a slow old age, and death necessarily follows. With time, their vessels become hardened, their size becomes reduced, they can no longer give passage to the sap, or other liquids which ought to go through them. Liquids are not aspired with the same regularity, they no longer transude through the vegetable tissue with the same precision; they remain stagnant in the vessels, become corrupt there, and transfer their decomposition to the vessels which enclose them. Thenceforth the vital functions cease to be performed, and the plant dies. Things happen in a like manner among animals. The thickening of the vessels, the decrease of their power bring on the condition of old age, in which the functions are disturbed and slackened; then comes death, the inevitable end of all, in each kingdom of nature.
Thus, when we compare animals and plants, and especially when we consider the inferior beings in both kingdoms, it is impossible to establish a precise line of demarcation between them. The characteristics by which the old naturalists defined the distinction between plants and animals, are now acknowledged to be without meaning, and this distinction becomes more and more difficult in proportion as we make progress in our knowledge of these creatures. Voluntary motion was regarded as the principal distinctive characteristic between the two kingdoms of nature; but at the present day this characteristic can no longer be invoked. Elementary works on botany now tell us about the fly-catching plant, which catches the insect that crawls over its leaves, exactly as a spider catches flies, and about the oscillating plant, whose leaves are endowed by voluntary motion, more distinct than that belonging to many animals.
Apart from these examples, drawn from classical works, we would ask what becomes of the argument for the immobility of plants, considered as a distinctive characteristic of the vegetable kingdom, when we see that zoophytes are fixed to the earth, and when, on the other hand, we see certain young plants, or their germs, such as the germs of algæ, mosses, and ferns, possessing the faculty of motion.
The spores, or reproductive organs of algæ, and the impregnating corpuscles of the mosses and ferns, possess the fundamental characteristics of animality, that is to say, they are provided with locomotive organs, and they execute movements which appear to be voluntary. Those singular creatures are seen to go and come in the interior of liquids, to endeavour to penetrate into cavities, to withdraw, return, and definitively introduce themselves with an apparent effort.
The German botanists regard these vegetable germs as belonging to the animal kingdom. Considering that only animals have the organs of motion, and that the spores of algæ and the impregnating corpuscles of mosses and ferns are provided with organs of motion, they do not hesitate to declare that in the commencement of their life, algæ, mosses, and ferns are in truth animals, which become plants when they fix themselves, and begin to germinate. French botanists have not yet ventured to adopt that view; they are content to call the movable impregnating corpuscles of algæ, mosses, and ferns, antherozoïdes, but they do not dare to pronounce upon their animality. M. Pouchet says, in his work L'Univers, page 444:
"Motion manifests itself spontaneously with extraordinary intensity in the animalculæ of several plants, which have spinal organs for this purpose, hairs by means of which they swim about in the liquid which contains them.
"Some of these, real animalcule plants, have the shape of eels, and move themselves by means of two long filaments attached to their heads; others exactly resemble the tadpoles of frogs, and jump about in the cells of the mosses.
"Nevertheless, it is such creatures as these, whose locomotive organs are so plainly to be discerned, and which we can see, under the microscope, jumping about as nimbly as our acrobats, that certain botanists persist in considering, on theory alone, as motionless and insensible. Some philosophers certainly possess eyes, that they may not see!"
There are these germs of plants, and young plants which move, and on the other hand, almost all the adult zoophytes, sponges, corals, madrepores, sea-stars, byssus, &c., &c., to which we may add several mollusca (all those in shells), are fixed to the earth. In these cases we must take the plant for the animal, and the animal for the plant, if we positively hold by voluntary motion as an absolute distinction between animals and plants.
On the borders of the two kingdoms,—when we consider zoophytes in the animal, and cryptogams in the vegetable kingdom,—there is no longer, so to speak, either animal or plant; the two seem to be confounded, and fused together.
If, before the discovery of the fresh-water polype, that living creature had been presented to a naturalist, he would have felt puzzled how to class it. Seeing it multiplying itself by buds, by offshoots, by engraftment, he would doubtless have declared that this organized being was a plant. But if he had been made to remark that this same creature fed on living prey, which it seized and swallowed, that it had long and flexible arms, of which it formed a kind of net for the purpose of seizing this prey, which it conveyed into the interior of a digestive tube, our naturalist would have made haste to place the polype in the ranks of the animals. He would have been asked to observe that the polype may be turned inside out, like a glove, so that his interior skin becomes his exterior skin, and that, thus turned inside out, he lives, grows, and multiplies himself, precisely as he does before this curious reversal. Our naturalist, much embarrassed in the presence of so unheard of a fact, would doubtless immediately have begun to seek some intermediate kingdom between the animal and the vegetable, to which he might relegate this paradoxical being, which could not, with absolute certainty, be classed either with plants, or with animals.
The fact is, classifications are products of human science, nature knows nothing about them. We descend, by insensible degrees, from one kingdom to the other; we go from the man to the polype, and from the polype to the rose tree, by infinite gradations, and, on the confines of the two kingdoms, there is a whole series of creatures which it is very difficult to range under any system. For how long did naturalists hesitate before they regarded infusoria, coral, sponges, star-fish, gorgons, sea-anemones, and madrepores as animals? Even in the present day micrographers who study the microscopic beings proper to vegetable and animal infusions, such as the monads, polypoid worms, and numerous others, find the utmost difficulty in assigning these creatures to such or such a kingdom, and they sometimes decide rather arbitrarily upon placing them among animals or plants.
From all the considerations, all the facts which we have just advanced, we conclude that the sensibility of plants is not to be contested, since no one can think of denying that privilege to certain zoophytes which can with difficulty be distinguished from vegetables.
We see an imposing tree, a stately oak with sturdy branches, growing on the sea coast. Not far off, on the sand of the shore, lies a star-fish flung there by the waves. A few yards below, on the surface of the water, floats a sponge, a branch of coral, a madrepore. When the icy wind blows, when the hurricane lifts the angry waves, which is it, the animal or the plant that will manifest sensibility to the tempest? The sponge, the coral, the madrepore will remain as indifferent to the fury of the elements as the rock in which they are incrusted, or as the pebble on which the star-fish stretches out its four motionless arms. But, the majestic oak will shudder at every gust of the tempest; he will bend his branches and shut up his leaves to shelter himself from the icy blast or the furious storm; and a mere glance at his attitude will indicate to you that an abnormal perturbation reigns in the atmosphere. Would you seriously say, in that case, that the vegetable feels nothing, and that the animal is sensible? Would you not, on the contrary, be inclined to declare that the tree is the sentient being, and that the star-fish, the sponge, the madrepore, are the creatures which are destitute of feeling?
Pause beside still water and seek for the polype or fresh-water hydra which we have just mentioned. You will find it difficult to disentangle this zoophyte from the reeds and willows which surround it. You will find, at length, a kind of membranous tube, a few centimetres in length. Is that the polype you were looking for? Is it not rather the stubble of some reed or grass plant? This living twig, with nothing to distinguish it in appearance from a herbaceous plant, is constantly fixed in the same place, like an aquatic vegetable. It makes some faint movements, consisting simply of the opening and shutting of the orifice of the tube, which solely constitutes its being. Sometimes it lengthens, sometimes it contracts itself, by stretching out membranous arms, as fine as threads, by means of which it seizes and drags towards it the water insects which chance to pass near it. This is the one single characteristic of its animality. At this rate, an aërial plant, the fly-catcher, would be just as much an animal as our polype, since it catches the insects which venture to crawl upon its leaves.
At the bottom of the sea there is a very curious zoophyte, the actinium, or sea-anemone. For a long time this creature was confounded with the plants, and held to be an ocean flower. Those who admire the beautiful, bright-coloured actinia, in the Garden of Acclimatization, in Paris, who look at them, waving on their flexible stem, shaking the coloured appendages and fringes which adorn their heads, find it hard to regard these charming queens of the waters otherwise than as real flowers. And, in fact, for ages, the sea-anemones were held to be marine plants.
In the last century, coral was held to be a marine shrub, and it was even believed that the flowers of the coral had been discovered. An academician of Paris, Count de Marsigli, created a European reputation for himself by this supposed discovery. Peyssonnel, a Provençal naturalist, found the utmost difficulty in opposing this idea, and in establishing the fact that these supposed flowers of the coral were in reality young corals. He had the whole Academy of Sciences against him; and his opposition to the ideas of the Academy brought him into such disgrace, that he was obliged to leave France and to go to the Antilles, where he died in obscurity as a doctor of medicine. And all this because he maintained that coral is not a plant, and does not produce flowers!
The famous Genevese naturalist, Charles Bonnet, anticipating the knowledge of our day by more than a century, has given a most interesting form to the parallel between animals and plants, in his work entitled Contemplation de la Nature. We cannot resist the pleasure of quoting the following passage, in which Charles Bonnet shows in a striking manner what are the difficulties in the way of distinguishing the plant from the animal, and how those difficulties are disposed of by those who dispute the sensibility of plants:—
"Everything is graduated in nature," says Charles Bonnet, "and, in refusing to admit that plants are sentient, we force nature to make a jump without any assignable reason.
"We observe that feeling decreases by degrees from man to the nettle, and to the mussel, and we persuade ourselves that it stops there, because we regard these animals as the least perfect. But there are, perhaps, many degrees between the feeling of the mole and of the plant. There are, perhaps, still more between the most and the least sensible of the plants. The gradations, which we observe, ought to persuade us to this philosophy; the new beauty which it adds to the system of the world, and the pleasure to be derived from the multiplication of sentient creatures ought to contribute to induce us to admit it. I willingly admit that this philosophy is much to my taste. I love to think that those flowers which adorn our fields and our gardens with a brightness constantly renewed, those fruit trees which are so pleasant to our eyes and our palate; those majestic trees that compose the vast forests, which time seems to have respected, are so many sentient creatures partaking after their fashion in the sweetness of existence.
"Plants offer some facts to our observation which seem to indicate that they possess feeling, but we are not likely to perceive those facts, because of the strong persuasion that they are insensible, which has prevailed among us for so long. We ought to agree to consider the question tabula rasa, and to subject plants to a new, impartial, and unprejudiced examination. An inhabitant of the moon, possessed of intellectual faculties like ours, but without any preconceived ideas about the insensibility of plants, would be the philosopher whom we require. Let us imagine such an observer engaged in studying the productions of our earth, and, after having given his attention to the polypes and other insects multiplied by the process of grafting, passing on to the contemplation of vegetables. He would, doubtless, take them at the period of their birth. With this view, he would sow seed of various species, and he would carefully watch their germination. Let us suppose that some of those seeds have been reversed in the sowing, the sprouting part turned downwards, the stem upwards; and the observer has the skill to distinguish one end of the seed from the other, and knows their functions. After some days, he will remark that the seed has grown into this reversed position, that the stem is turned upward, and the sprouting portion downward. He will feel no surprise; he will attribute a circumstance which is so hurtful to the life of the plant, to the mistake he has made in sowing the seed. But, continuing to observe, he will see the sprout and the stem each bending itself in the opposite direction, and trying to attain the right position. This change of direction will strike him as very remarkable, and he will begin to suspect that the organized being which he is studying is endowed with a certain amount of discernment. Too prudent, however, to pronounce upon these early indications, he will suspend his judgment and pursue his investigations. The plants whose germination our physicist has been observing, have been raised in the neighbourhood of a hedge. Thus favoured, and carefully cultivated, they have made great progress in a very short time. The soil which surrounds them at some distance is of two opposite qualities. That on the right of the plants is rich, damp, and spongy; that on the left is dry, hard, and gravelly. Our observer remarks that the roots, after having begun by extending equally on both sides, have changed their direction, and have spread out towards the rich and humid soil; over which they are stretching, and thus threatening to deprive the plants already there of their due share of nourishment. To prevent this inconvenience, he digs a ditch between the plants which he is observing and those they threaten to starve, and now he thinks he has provided against everything. But the plants, which he believes he has governed, disconcert all his precautions by extending their roots downwards, under the ditch, and gaining the other side.
"Surprised at this, he uncovers one of these roots, but without exposing it to heat, and holds a sponge steeped in water towards it. The root turns itself to the sponge, and when he changes its position, the root accommodates itself to each alteration.
"While our philosopher is meditating profoundly upon these facts, other facts equally remarkable present themselves almost simultaneously. He observes that all these plants have leaned away from the hedge, and are bending forward as though to present every portion of their bodies to the beneficent smiles of the sun. He sees that all the leaves are so turned that their upper surface is exposed to the sun, or to the fresh air, and that the lower surface is directed towards the hedge, or the ground. Former experience will have taught him that the upper surface of leaves serves chiefly as a defence for the lower surface, and that the latter is principally destined to pump up the moisture rising from the earth, and provide for the evacuation of what is superfluous. The direction of the leaves which he notices appears quite in harmony with his experiences. He studies this portion of the plant with increased attention.
"He remarks that the leaves of some species seem to follow the movements of the sun, so that in the morning they turn to the east, in the evening to the west. He sees that some leaves close themselves against the sun, others against the dew. He observes an analogous movement in certain flowers. Afterwards, he observes that no matter what the direction of the plants relative to the horizon has been, the direction of the leaves is always that which he has at first noticed, he bethinks him of changing this direction, and of placing the leaves in a position exactly contrary to their natural one. He has already had recourse to similar means in order to assure himself of the instinct of animals, and to ascertain its bearings. With this view he bends perpendicular plants towards the horizon, and keeps them in that position. Thus, the direction of the leaves is absolutely changed; the upper surface, which previously turned to the sun or to the fresh air, now looks towards the earth or the interior of the plant, and the lower surface, which formerly looked towards the earth or the interior of the plant, now turns to the sun, or the fresh air. But very soon all these leaves begin to move, they turn on their stem as on a pivot, and in an hour they will have resumed their former position. Our observer, wishing to assure himself whether leaves and branches when detached and plunged into water will preserve the inclinations which they manifest when upon the plant of which they formed a portion, subjects them to an experiment whose results leave him no doubt of the fact.
"He places wet sponges under the leaves, and he sees the leaves turn towards the sponges and endeavour to adhere to them by their lower surfaces. He also observes that certain plants, which he has shut up in his cabinet and in a cellar, have turned towards the window, or the grating respectively.
"Finally, the phenomena of the Sensitive Plant, its varied movements, the promptitude with which it contracts when touched, form the interesting subject which terminates his researches.
"Thus plentifully supplied with facts which all seem to tend to the support of belief in the sensibility of plants, which side will our philosopher take? Will he surrender to these proofs? Will he suspend his judgment? I think he will take the first part."[16]
Charles Bonnet believes, in short, that the plant, as well as the animal, is endowed with sensibility.
According to the system which we have developed, the animal is possessed of a soul, which is still very imperfect, and endowed only with faculties corresponding to its needs. But, since the animal, in addition to the sensibility enjoyed by the plant, possesses intelligence also, we must conclude from thence that the plant has not a soul, properly so called, but only the rudiment, the commencement, in other words, the germ of a soul.
We know that the sun has the privilege of giving birth to organic life upon our globe, his rays have power to produce the formation of living tissues, plants or zoophytes, when they fall upon the earth or the waters, and we may draw this conclusion from all that has gone before, that the sun sends down upon the earth animated germs under the form of his rays, which emanate from the spiritualized creatures who dwell in the king-star.
Thus our system of nature completes itself; thus, thanks to solar radiation, the two ends of the immense chain of organized beings whose place and part in the vast theatre of the worlds we have attempted to define are united. Life begins in the waters, its first appearance is in plants and zoophytes; for these two classes of living creatures obey the same laws, and appear to have the same origin. The sun, by sending his vivifying rays upon the earth, produces the formation of plants and zoophytes, which are the points of departure of organization. The animated germ deposited by the sun in plants and zoophytes grows, passes from the zoophyte to the mollusc, or articulated animal, and then undergoes a further development, by passing from the mollusc or articulated animal to the fish. This germ of a soul thus becomes a rudimentary soul, provided with certain faculties. In the zoophyte and the mollusc it had only sensibility; in the fish, and then in the reptile, and the bird, it has attention and judgment. The faculties are augmented in proportion as the animal mounts higher in the organic scale. Arrived at its summit, the human being, the soul is in possession of all its faculties, and especially of memory, which during the animal stages of the ascent is obscure and uncertain.
To accord sensibility to plants permits us to unite all the creatures of the living creation, and thus to complete our general system of terrestrial nature.
