OF THE VASA PROPRIA INTIMA.
These are the only vessels which remain to be spoken of. They are large, conspicuous, and important; their natural place is in the blea, though they are sometimes repeated in the wood and the corona. Their coats are thicker than those of any other vessels.[141] It is not difficult, after a successful maceration, to separate some of these vessels from the blea; in this state they appear perfect cylinders, with thick white coats, of a firm, solid, and uniform texture.
[141] Hill’s Construction of Timber, p. 83 and 85.
It has generally been supposed, that each of those concentric circles, which are to be observed in the transverse section of almost every tree, was the product of one year, or the quantity of wood added to the tree in that space; here, however, Dr. Hill differs again from the general opinion.
From what has been said, we may deduce the following general ideas relative to the organization of trees. The most obvious and remarkable parts of a plant, or tree, are the root, the stem, the branches, the leaves, the flower, and the fruit. The component parts of these divisions are not complicated; they are simple when compared with those of an animal, and this because the offices of the vegetable are fewer than those of the animal.
The interior part may be considered as consisting of ligneous fibres, interspersed with a vast number of bladders, which are here named the cellular tissue, the vasa propria, and the sap vessels; though these are considered by some writers as mere air vessels.
The ligneous fibres are very fine tubes, proceeding nearly in a vertical direction from the top to the bottom of the tree; they are sometimes parallel to each other, sometimes they divaricate, and often leave oblong intervals or spaces. There is great reason for supposing them to be a species of lymphatic vessels. The vacant spaces between these fibres are filled up by a vesicular membrane, lying in an horizontal direction, and which is called in this chapter the cellular tissue.
The vasa propria are formed of ligneous fibres, but differ from the foregoing in their size, and in the juices which they contain. In the part properly called the wood, we meet with the sap vessels; but as in some states they seem as if they were formed of a silver-coloured spiral membrane, and are found without any juices, they have been supposed to be air vessels, and called the trachea, making up an arterial system, and supplying the place of the heart in animals.
The interior part of the tree may be further considered as divided into four principal concentric strata, the bark, the blea, the wood, and the pith; to these Dr. Hill has added the corona. Whatever part of a plant is examined, we find these and no more. The root, its ascending stalk, and descending fibre, are formed of one, and not three different substances. Thus the whole vegetable is reduced to one entire body. And what appears in the flower to be formed of altogether distinct parts, will be found to originate in these.
The bark, which is the exterior covering of the tree, is divided into two parts, a thin outer rind, and a much thicker inner one. The exterior one seems to be little more than a fine film of irregular meshes, the inner one composed of large blebs, leaving in some subjects large vacant spaces, which form its vasa propria. It is made up of several strata lying one over the other.
Next to this is the blea, which is of an uniform structure. It is an imperfect wood, waiting only for the hand of time to be brought to perfection. The duration of the blea in this middle state depends on the internal powers and strength of the tree, being so much shorter as this is more vigorous.
The wood, including the corona, comes next; it differs in density and duration both from the blea, the bark, and the wood. It is made up of strong fibres. The life of the vegetable seems to reside in it; from it all the other parts are produced. It shoots a pith inwards, and a blea and a bark outwards.
Every tree may be considered as consisting of numerous concentric strata or flakes, forming so many cones, inscribed one within the other, and whose number is almost indefinite. The most exterior contain the rudiments of the bark; the more interior, those of the wood. In the germ they are gelatinous, by degrees they become herbaceous, and in process of time assume the consistence of wood. Thus the stem, the root and the branch, may be considered as formed of a prodigious number of concentric vertical strata, each composed of different fascicles of fibres; which fibres are again formed of smaller ones. The spaces between these, and among the fibres, are filled up, interwoven with, and connected by the cellular tissue, of which the radial insertions are formed.
The strata harden successively one after the other; the most interior stratum is that which hardens first; this is then covered by another which is more ductile and herbaceous, and so on; so that the bulk of the tree is increased every year by the accession of an hollow cylinder of wood derived from the internal bark. From the extension in breadth, the tree acquires bulk; from that in length it gains its height. The strata gradually diminish in size as they gain in length; from hence the conical figure of the root, stem, and branch. All the parts of the plant are the same, differing in nothing more than in shape and size. The roots are sharp and pointed, that they may make their way more readily through the earth. The leaves are broad, that they may more effectually catch the moisture from the atmosphere, &c. When the root of a tree is elevated above, instead of being retained under the earth, it assumes the appearance of a perfect plant, with leaves and branches. Experiment shews that a young tree may have its branches placed in the earth, and its roots elevated in the air, and in that inverted state it will continue to live and grow. The principal source of the phænomena of vegetation is the simplicity and uniformity of their organization.
The figures in [Plates XXVIII.] [XXIX.] and [XXX.] are portions of transverse sections of trees and herbs. The sections were cut by Mr. Custance,[142] who first brought this art to perfection, and remains hitherto unrivalled in these performances.
[142] For a collection of Mr. Custance’s vegetable cuttings, and which, in sets, usually accompany the best sort of microscopes, made by Messrs. Jones, see the list of microscopical objects now annexed to this work by the editor.
[Plate XXVIII.] Fig. 1, exhibits a piece of an herb growing on rubbish, and known by the name of fat-hen:[143] Fig. 2, a microscopic view of the same. Fig. 3, a magnified representation of a section of a reed that comes from Portugal: Fig. 4, the real size of the section.
[143] Chenopedium bonus Henricus.
[Plate XXIX.] Fig. 1, is a magnified view of a section of the althea frutex: Fig. 2, the natural size of the section. Fig. 3, a magnified view of a section of the hazel: Fig. 4, its natural size. Fig. 5, a microscopic view of a section of a branch of the lime-tree: Fig. 6 represents its natural size.
[Plate XXX.] Fig. 1, a magnified view of a section of the sugarcane: Fig. 2, its natural size. Fig. 3, a magnified view of a section of the bamboo cane: Fig. 4, the natural size. Fig. 5, a magnified view of a section of the common cane: Fig. 6, the real size.
CHAP. X.
OF THE CRYSTALLIZATION OF SALTS, AS SEEN BY THE MICROSCOPE; TOGETHER WITH A CONCISE LIST OF OBJECTS.
Crystallization, in general, signifies the natural formation of any substance into a regular figure, resembling that of a natural crystal. Hence the phrases of the crystallized ores, crystallized salts, &c. and even the basaltic rocks are now generally reckoned to be effects of this operation; the term, however, is most commonly applied to bodies of the saline kind; and their separation in regular figures from the water, or other fluid in which they were dissolved, is called their crystallization. If the word crystallization were to be confined to its most proper sense, as it seems to have been formerly, it could only be applied to operations by which certain substances are disposed to pass from a fluid to a solid state, by the union of their parts, which so arrange themselves, that they form transparent and regularly-figured masses, like native crystal; from which resemblance the word crystallization has evidently been taken.[144]
[144] Macquer’s Dictionary of Chemistry, Art. Crystallization.
But modern chemists and naturalists have much extended this expression, and it now signifies a regular arrangement of the parts of any body which is capable of it, whether the masses so arranged be transparent or not. Thus opake stones, pyrites, and minerals when regularly formed, are said to be crystallized, as well as transparent stones and salts.
The opacity and transparency of substances are justly disregarded, in considering whether they be crystallized or not; for these qualities are perfectly indifferent to the regular arrangement of the integrant parts of substances, which is the essential object of crystallization.
This being established, crystallization may be defined, an operation by which the integrant parts of a body, separated from each other by the interposition of a fluid, are disposed to unite again, and to form solid, regular, and uniform masses.
To understand as much as we can of the mechanism of crystallization, we must remark,
1. That the integrant parts of all bodies have a tendency to each other, by which they approach, unite, and adhere together, when not prevented by an obstacle.
2. That in bodies simple or little-compounded, this tendency of integrant parts is more obvious and sensible than in others more compounded; hence the former are much more disposed to crystallize.
3. That although we do not know the figure of the primitive integrant molecules of any body, we cannot doubt but that those of every different body have a constantly uniform and peculiar figure.
4. That these integrant parts cannot have an equal tendency to unite indiscriminately by any of their sides, but by some preferably to others, excepting all the sides of an integrant part of a body be equal and similar; and probably the sides, by which they tend to unite, are those by which they can touch most extensively and immediately.
The most general phænomena of crystallization may be conceived in the following manner:
Let a body be supposed to have its integrant parts separated from each other by some fluid; if a part of this fluid be taken away, these integrant parts will approach together: and, as the quantity of intervening fluid diminishes, they will at last touch and unite. They may also unite when they come so near to each other, that their mutual tendency shall be capable of overcoming the distance betwixt them. If, besides, they have time and liberty to unite with each other by the sides most disposed to this union, they will form masses of a figure constantly uniform and similar. For the same reason, when the interposed fluid is hastily taken away, so that the integrant parts shall be approximated, and be brought into contact before they have taken the position of their natural tendency, then they will join confusedly by such sides as chance presents to them; they will, in such circumstances, form solid masses, whose figures will not be determinate, but irregular and various.
Different salts assume different figures in crystallization, and are, by these means, easily distinguished from one another. But besides the large crystals produced in this way, each salt is capable of producing a very different appearance of the crystalline kind, when only a drop of the saline solution is made use of, and the crystallization viewed through a microscope. For our knowledge of this species of crystallization, we are indebted to Mr. Henry Baker, who was presented by the Royal Society with a gold medal for the discovery, in the year 1744. These microscopical crystals he distinguishes from the larger ones by the name of configurations; but this term seems inaccurate, and the distinction may be properly preserved by calling the large ones the COMMON, and the small ones the MICROSCOPICAL, crystals of the salt.
It has not yet been shewn by any writer on the subject, why salts should assume any regular figure, much less why every one should have a form peculiar to itself. Sir Isaac Newton endeavoured to account for this, by supposing the particles of salt to be diffused through the solvent fluid, at equal distances from each other; and that then the power of the attraction between the saline particles could not fail to bring them together in regular figures, as soon as the diminution of heat suffered them to act on each other. But it is certain some other agent must be concerned in this operation, besides mere attraction, otherwise all salts would crystallize in the same manner. Others have, therefore, had recourse to some kind of polarity in the particles of each salt, which determined them to arrange themselves in such a certain form; but unless we give a reason for this polarity, we only explain crystallization by itself. One thing seems to have been overlooked by those who have endeavoured to investigate this subject, namely, that the saline particles do not only attract one another, but they also attract some part of the water which dissolves them.
Did they only attract each other, the salt, instead of crystallizing, would fall to the bottom as a powder; whereas, a saline crystal is composed of salt and water, as certainly as the body of an animal is composed of flesh and blood, or a vegetable of solid matter and sap; if a saline crystal be deprived of its aqueous part, it will as certainly lose its crystalline form, as if it were deprived of the saline part. It is, therefore, not improbable, that crystallization is a species of vegetation, and is accomplished by the same powers to which the growth of plants and animals is to be ascribed. Some kinds of crystallization resemble vegetation so much, that we can scarce avoid attributing them to the same cause.
It has been imagined, that all the great operations in nature may be reduced to two principles, those of crystallization and organization; but that often they are so concealed, as to be invisible. Hence crystallized substances have been frequently mistaken for organized ones, and vice versa. They differ, however, essentially in their growth and origin. Organized beings spring from a germ, in which all the essential parts are concentrated, and they grow by intusception; whereas crystallized substances increase by the successive apposition of certain molecules of a determined figure, which unite in one common mass. Thus crystallized beings do not grow, properly speaking, though their substance is augmented, they are not preformed, but formed daily.
The phænomena of crystallization have much engaged the attention of modern chemists, and a vast number of experiments has been made with a view to determine exactly the different figures assumed by salts in passing from a fluid to a solid form. It does not, however, appear, from all that has yet been done, that any certain rule can be laid down in these cases, as the figure of saline crystals may be varied by the slightest circumstances. Thus, sal ammoniac, when prepared by a mixture of pure volatile alkali with spirit of salt, shoots into crystals resembling feathers; but if, instead of a pure alkali, we make use of one just distilled from bones, and containing a great quantity of animal oil, we shall, after some crystallizations of the feathery kind, obtain the very same salt in the form of cubes.
Such salts as are sublimeable crystallize not only in the aqueous way by solution and evaporation, but also by sublimation; and the difference betwixt the figures of these crystals is often very remarkable. Thus, sal ammoniac, by sublimation never exhibits any appearance of feathery crystals, but always forms cubes or parallelopipeds. This method of crystallizing salts by sublimation has not as yet been investigated by chemists; nor indeed does the subject seem capable of investigation without much trouble, as the least augmentation of the heat beyond the proper degree would make the crystals run into a solid cake, while a diminution of it would cause them to fall into powder. In aqueous solutions, too, the circumstances which determine the shapes of the crystals are innumerable; and the degree of heat, the quantity of salt contained in the liquor, nay, the quantity of the liquor itself, and the various constitutions of the atmosphere at the time of crystallization, often occasion such differences as seem quite unaccountable and surprizing.
Mr. Bergman has given a dissertation on the various forms of crystals; which, he observes, always resemble geometrical figures more or less regular. Their variety at first appears infinite; but by a careful examination it will be found, that a great number of crystals, seemingly very different from each other, may be produced by the combination of a small number of original figures, which therefore he thinks may be called primitive. On this principle he explains the formation of the crystalline gems, as well as salts.[145]
[145] Encycl. Britan. Vol. V. p. 583.
It has been already shewn, [page 163], how to prepare the various salts for microscopical observations. The beautiful crystallizations represented in [Plates XXXI.] and [XXXII.] were produced in the manner there described.
[Plate XXXI.] Fig. 2, exhibits a view of the microscopical crystals of nitre. These shoot from the edges with very little heat, in flattish figures, of various lengths, and exceedingly transparent, the sides nearly parallel, though rather jagged, and tapering to a point; after a number of these are formed, they often dissolve under the eye, and disappear entirely; but in a little time new shoots will push out, and the process go on afresh. Beautiful ramifications are formed round the edge, and many regular figures are to be observed in different parts of the drop. Fig. 1 is the real size of the drop.
Fig. 4 is a drop of distilled verdigrise, as it appeared when viewed by the microscope. There is a difference in the appearance from this substance, according as the time of the application is nearer to, or more distant from that in which the solution was made. Fig. 3, the size of the drop.
If a drop of distilled verdigrise upon glass be viewed through the microscope, after the crystallization is completed and the water evaporated, there remains a substance round the crystallization, which preserves the original size and shape of the drop when a liquid; betwixt this verge of the drop and the crystals fine lines are discernible running from the crystals to the circumference of the drop, at various angles with the crystals; whatever direction they take, they are always perfectly straight, and of an equal thickness throughout. When the drop is viewed through a light ground, these lines appear dark; but when viewed through a dark ground, they then shine and appear of the beautiful green colour natural to the crystals of verdigrise.
[Plate XXXII.] Fig. 1, represents the microscopical appearance of the crystals of salt of wormwood. The shootings from the edges of this solution are often very thick in proportion to their length, their sides full of notches, the ends generally acute; many spear-like forms are also to be observed, as well as little crystals of a variety of figures.
Fig. 2. Salt of amber. The shootings of this salt are highly entertaining, though the process is very slow; many spiculæ shoot from the edge towards the middle of the solution, and from the pointed ends of the spiculæ a great variety of diversified branches may be observed, variously divided and subdivided, and forming at last, says Baker, a winter scene of trees without leaves.
Fig. 3. Salt of hartshorn. This salt shoots out from the edge of the drop into solid, thick, and rather opake figures; from these it often shoots into branches of a rugged appearance, similar to those of some species of coral.
Fig. 4 represents the microscopical crystals of sal ammoniac. These form a most beautiful object in the microscope; a general idea may be more easily acquired by attentively viewing the figure here exhibited, than by any verbal description.[146]
[146] A collection of salts, as recommended by Mr. Baker, properly prepared and packed in portable boxes by Messrs. Jones, the reader will see in the extensive [list] of microscopic objects now annexed to this work by the editor.
A
CONCISE LIST OF OBJECTS
FOR
THE MICROSCOPE.
The short list here presented to the reader must, from the nature of the subject, be very imperfect; for the whole of the animal, vegetable, and mineral kingdoms, with all their numerous subdivisions, furnish objects for the microscope; and there is not one of them, that, when properly examined, will not afford instruction and entertainment to the rational investigator of the works of creation. The Systema Naturæ of Linnæus may therefore be regarded as a catalogue of universals for microscopic observation, each of which comprehends a variety of particulars. The list here given can be considered as little more than a directory, to point out to those who have only begun to study this part of natural history a few of those objects which merit their attention, and which, from their beauties, may incite them to pursue the study with greater ardor.
OF OPAKE OBJECTS.
Ores and minerals afford an immense variety of very beautiful and splendid objects. From amongst these the observer may select the peacock or coloured copper ore, green crystallized ditto, lead ore, crystallized ditto, crystals of lead, small grained marcasites, coloured mundic, cinnabar, native sulphur, needle and other antimony, moss copper, &c. A mixture of small pieces of ores, &c. of different kinds, produces a pleasing effect. Sands in general exhibit something not discoverable with the naked eye. Sand from the sea-shore is often intermixed with minute shells, particularly that from Rimini, in Italy. Mr. Walker has published a specimen of the small microscopic shells which are found on our own coast. From this work we learn, that there are shell-fish as small as the minutest insects, and possessed of beauties of which we can form no conception till we have seen them. Mr. Walker’s work is entitled, “A Collection of the minute and rare Shells lately discovered in the Sand on the Sea-shore near Sandwich.”[147] There is a sand from Africa full of small garnets. The ketton, or kettering stone, is a pleasing object; when examined by the microscope, we find the grain of it very different from that of other stones, being composed of innumerable minute balls, which barely touch each other, and yet form a substance much harder than free-stone; the grains are, in general, so firmly united together at the points of contact, that it is hardly possible to separate them without breaking one or both of the grains. See Hooke’s Micrographia.
[147] This publication will be more particularly noticed in the ensuing [chapter]. Edit.
Insects of all kinds, both foreign and domestic, are pleasing objects; but as the foreign ones are not so easily met with, I shall mention but a few of them, confining myself principally to those of this country. Among the exotic insects, none appear more beautiful in the microscope than the curculio imperialis, Brazil or diamond beetle; the buprestis ignita, or large beetle from China; the meloe vesicatorius, Linn. the cantharis or Spanish fly of the shops; several species of locusts, grasshoppers, &c. Among the English beetles, we may reckon the scarabæus auratus or rose chaffer, scarabæus nobilis, scarabæus horticola, silpha aquatica, cassida nobilis and nebulosa. Coccinella or lady-cow; of these there are great varieties both in size and colour, some red and black, others black and red, and some yellow and black. Chrysomela graminis, chrysomela fastuosa, chrysomela nitidula, chrysomela sericea, chrysomela melanopa, chrysomela asparagi, see [Plate XX.] Fig. 2. Curculio frumentarius, lapathi, betula, nucum, scrophularia, argenteus, a beautiful little insect resembling the diamond beetle, but in miniature; curculio albinus, very beautiful, but scarce in this country. Leptura aquatica, these are of various colours, as blue, purple, bronze, and crimson. Arcuata arietis, very common, and is often called the wasp beetle. Cicindela campestris, on dry banks. Carabus nitens, found in Yorkshire, a beautiful insect; many small carabi. Gryllus, gryllo-talpa or mole cricket, this insect, and the grasshoppers, are many of them too large to be observed at one view, but the head, fore and hind feet, elytra, &c. viewed separately, are fine objects. Cicada sanguinolenta, nervosa, interrupta, notonecta striata, minutissima, head and claws of the nepa cinerea or water-scorpion, and the whole variety of cimices or field bugs. The wings of butterflies and moths; the chrysalis of the common white butterfly is extremely fine.
I wish it were in my power to invite the reader to consider the pupa state of these insects, as he would find them interesting in various points of view. Perhaps the following passage from an ingenious writer may have this effect.
“Some of these creatures crawl for a time as helpless worms upon the earth, like ourselves; they then retire into a covering, which answers the end of a coffin or a sepulchre, wherein they are invisibly transformed, and come forth in glorious array, with wings and painted plumes, more like the inhabitants of the heavens than such worms as they were in their former state. This transformation is so striking and pleasant an emblem of the present, the intermediate, and glorified state of man, that people of the most remote antiquity, when they buried their dead, embalmed and inclosed them in an artificial covering, so figured and painted, as to resemble the caterpillar in the intermediate state; and as Joseph was the first we read of that was embalmed in Egypt, where this custom prevailed, it was probably of Hebrew original.”
The eggs of moths and butterflies, particularly the phalæna neustria, see [Plate X.] Fig. 1 to 6. The bodies and heads of many libellulæ.
Many of the ichneumon flies, spheges, and wasps, head of the hornet, sting of ditto, collectors of the bee, many sorts of muscæ, or flies with two wings, especially those whose bodies are highly coloured; acari or ticks; phalangium cancroides, see [Plate XVIII.] Fig. 1 and 6. Some spiders, but the eyes of all; the oniscus or wood-louse, julus, and scolopendra.
The feathers of peacocks, and many other birds, have a grand effect when viewed in the opake microscope, as have also some species of ferns, mosses, and wood cut transversely. Madrepores, millepores, sponges, corallines, &c. exhibit wonderful appearances not discernible to the naked eye. Parts of echini or sea eggs, spines of ditto; these may also be cut transversely to shew their construction. Minute shells dissected, skin of many species of fish, particularly the lump-sucker, see [Plate XVIII.] Fig. 2. Sole fish, [Plate XIX.] Fig. 5. and the rasp fish from Otaheite; also the skins of snakes, lizards, guanas, &c. &c.
The exterior form, and even the interior structure of the generality of vegetable seeds, have been supposed by some so much alike in the several kinds, and of so little curiosity and beauty in the whole, that they have scarcely been regarded by the curious; but when nearly examined with the help of microscopes, they are found to be worthy of a greater attention; those which appear most like to one another when viewed by the naked eye, often proving as different, when thus examined, in their several forms and characters, as the different genera of any other bodies in the creation. If their external forms carry all this variety and beauty about them, their internal structure, when laid open by different sections, appears yet more admirable.
The seed of the greater maple, which we commonly, but improperly call the sycamore tree,[148] consists of a pod and its wing; two of these grow upon a pedicle, with the pods together, which makes them resemble the body of an insect with its expanded wings: the wings are finely vasculated, and the pods are winged with a fine white down resembling silk; this contains a round compact pellet, covered with a brown membrane that sticks very closely to it. When this is pulled off, instead of discerning a kernel, as in other seeds, there appears an entire green plant folded up in a most surprizing manner. The pedicle of this is about two-eighths of an inch long, and its seminal leaves of about six-eighths each; between these the germina of the next pair of leaves are plainly visible to the naked eye, but with a microscope they are seen with the greatest beauty and perfection.
[148] The Acer pseudo-platanus, Hudsoni Fl. Angl. p. 445. Parkinson calls it acer majus, adding, sycomorus falso dictum. Hudson, however, agrees with Hunter in his edition of Evelyn’s Sylva, in affixing to it the English term greater maple or sycamore. Edit.
The seed of the musk scabious is beautiful in its shape and structure. The calix or cup which contains the seed is of an octagonal form, and makes an appearance like a fine vase, having scallopped edges, and toward the inner part of the edge a white ruffled membrane. The ribs run down from its mouth, which is bell-fashioned, and becoming narrower downward, form obtuse angles by continuing from the bend to form the bottom of the vase. Between these ribs, down to the beginning of the narrow part, it is clear, though not wholly transparent, and from thence to the bottom the ribs are hairy. This vase contains the seed, wherein appears first its thick body, which runs up with a narrow neck, till it divides into five spiculated fibres, whose spiculæ are determined upwards, and are thereby prepared to cause the seed to recede from any thing that might injure it on being touched. The bodies of the vases, when first ripe, are of a fine lemon yellow, but grow by long keeping darker; and the bason formed by the roots of the minute fibres is of a fine green, but the fibres themselves of a shining brown, like brown sugar-candy, as their spines are also.
These, and a number of similar beauties in this part of the creation, are described at large by Dr. Parsons, in his work entitled, “The Microscopic Theatre of Seeds.”[149] Most kinds of seeds should be prepared for a microscopical examination by steeping them in warm water till their coats are separated, and their seminal leaves may then be opened without laceration. But seeds, while dry, and without any preparation, are of an almost infinite variety of shapes, and afford a number of pleasing objects for the microscope.
[149] This curious work was published in the year 1745. It was the author’s intention to have comprised the whole design in four volumes quarto, but the first volume only appeared. It contains the etymology, synonyma, and description of the several plants and their flowers, with an account of their medical virtues, and an explanation of botanical terms. As the work is in but few hands, and a copy not easy to be procured, I flatter myself that extracts from those parts containing the microscopical descriptions will form an agreeable addition to these Essays; which the reader will accordingly meet with in the following [chapter]. Edit.
One of the most interesting scenes in microscopical botany is exhibited in mouldiness. Those miniature plants seem to bear the same relation to the vegetable kingdom that the animalcula infusoria do to the animal; they were formerly considered as shapeless and unformed masses, but we now view them with surprize and pleasure taking their place in the great scale of organized beings, and presenting us with some of the most striking characteristics of vegetables.
OF TRANSPARENT OBJECTS.
We may select from the elytra, or upper wings of beetles, many beautiful objects, the construction of these will be found to differ very much; the membranaceous wings, as in the scarabæus solstitialis or small cock-chaffer; blatta Americana or cockroach; all the grylli, as locusts, grasshoppers, &c. Among the cicadas, the elytra of the nervosa are the most elegant, the nerves are elevated, and curiously spotted with brown. The elytra of the cimices or field bugs, which are a very numerous tribe, afford a great variety of objects; we may select from these as the most beautiful the elytra of the cimex baccarum and the cimex striatus, [Plate XX.] Fig. 1. The elytra of the fulgora candelaria, from China, differ essentially from all others.
The under or more transparent wings of beetles excite our attention even more than the upper or crustaceous ones; for whether we consider the delicacy of their texture, the great weight that many of them are calculated to sustain in the air, or the very curious manner in which they fold them up under the upper case, their mechanism must astonish and delight us; no two genera will be found alike, though every individual of the same genus will be exact. The wing of the forficula auricularia or earwig, [Plate XIV.] is an elegant specimen of the manner of their folding; this wing folds under a case not one-eighth of its size.
The under wing of the blatta orientalis, or beetle common in most kitchens, appears to unite the elytra and transparent wings, partaking in some degree of both.
Among the membranaceous or more transparent winged insects, the variety is endless, each genus differing essentially from the other; some appearing full of membranes or nerves, curiously disposed; others, again, with scarce any, like a clear piece of talc or isinglass; some exhibit a curious ground-work of points, which on close examination prove short hairs, while the nerves of others are furnished with little scales or feathers, as in some species of the gnat. The wings of many muscæ are coloured with black, brown, and white, in clouds, spots, stripes, &c. &c.
The libellulæ or dragon-flies alone afford a great variety, not only in form but colour; these are all furnished with numerous and very strong nerves, adapted to the velocity of their flight. The wings of the ephemera or may-flies, are much more delicate, these flies rest with their wings erect. The phryganeæ differ very much from the foregoing, and also from one another; their under wings fold, and their upper ones are of a stronger texture, many of them so much resembling small moths as not easily to be distinguished from them: these are all found in the vicinity of ponds and marshy places. In the hemerobii a wonderful degree of elegance is exhibited in the disposition of the nerves which compose their wings, each nerve being adorned with hair in a beautiful manner; there are many species of these flies equally beautiful, a specimen is given in [Plate XV.] The ichneumon fly has four transparent wings, the inferior ones smaller, and more delicate than the superior; the tube through which the female deposits its eggs is an additional object well worth attention. The wings of wasps are folded longitudinally; the wings of the large bee are very curious. Gnats in general, and the various species of tipulæ, together with the clouded and variegated wings of the muscæ, tabani, &c. increase the catalogue beyond the power of enumeration; in short, there is not a wing but has its particular beauties, and will amply repay the attentive observer. The currant sphinx moth connects the transparent and farinaceous wings, partaking of both; the white plumed, and many-plumed moths, exhibit wings totally different from all the rest; many other small moths furnish wings sufficiently transparent for observation, the fringe or edges being remarkably beautiful.
OF THE PULEX IRRITANS, OR COMMON FLEA.
Many small insects that are not too opake, may be viewed and examined as transparent objects; some of these having been particularly noticed by the early microscopic writers, it will be necessary to enumerate a few of them, as without it the work might be deemed incomplete. Every one is acquainted with the agility and blood-thirsty disposition of the flea, of the caution with which it comes to the attack, and the readiness with which it avoids pursuit. It belongs to the class aptera, has two eyes, six feet particularly constructed for leaping, the antennæ or feelers are filiform, or rather moniliform; the rostrum is inflected, setaceous, and armed with a sting; the belly is compressed. This creature is produced from eggs, which it deposits on the animals that afford it food, or affixes them to the wool of blankets, rugs, &c. These eggs in about a week are hatched into small larvæ or worms, which are of a whitish colour, with a slight tinge of reddish, and adhere closely to the body of the animal, or other substance on which they are produced; in a fortnight they come to a tolerable size, and are very lively and active; but if they be touched, they roll themselves up in a ball. At this period they prepare themselves for their pupa or chrysalis state, by inclosing themselves in a loosely-spun web, or diffused envelopement of a very soft, silky, or rather cotton-like appearance, and of a white colour. In this the larva changes into a chrysalis, out of which in about twelve days emerges the animal in its perfect state, armed with powers to disturb the peace of an emperor, and occasion uneasy sensations in the fairest bosom.[150]
[150] Notwithstanding the inconveniences attending this little insect, and the general disapprobation which its frequent intrusion occasions, there is something pleasing in the appearance of the flea; all its motions are elegant, and all its postures indicate agility. The shelly armour in which it is enveloped, is in a state of perpetual cleanliness; while the muscular power which it is capable of exerting is so extraordinary, as justly to excite our wonder at so much strength confined, and concentrated as it were, in so small a space.
The flea, like many other insects, is eminent for its powers of revivescence, and will frequently recover after being placed in situations very unfavourable to animal life. Some of the coleopterous insects are, however, capable of exhibiting far more striking examples of suspended animation. Nat. Misc. vol. v. Edit.
It is difficult to obtain such a view of the flea, as will display the mechanism and apparatus belonging to the head; these parts are but imperfectly represented in the celebrated drawing of Dr. Hooke in his Micrographia. The neck is long, finely arched, and much resembles the tail of a lobster; the body is covered all over with a polished suit of sable armour, formed of a hard shelly substance, curiously jointed and folded over one another, and yet yielding to all the nimble motions of the little animal; the edges of the scales are curiously set with short spikes or hairs: it has two sharp eyes to look before it leaps, for which purpose its legs are excellently adapted, having three large joints in each, besides several smaller ones. These joints are so contrived, that it can as it were fold them up one within another; in leaping, they all spring at once, and the whole strength of the insect is exerted. The flexure of the fore legs is forward, that of the hind legs backward. They are all very hairy, and terminated by two long hooked sharp claws; the two fore legs are placed very near the neck, and often conceal the proboscis from our view, the other four join all at the breast: the proboscis or sucker with which it penetrates the skin, is placed at the end of the snout, and is not easily seen except the two fore legs are first removed; in it are included a couple of darts or lancets, which, after the proboscis has made an entrance, are thrust farther into the flesh, and make the blood flow from the adjacent parts, occasioning that round red spot, with a hole in the center of it, called a flea-bite.
OF THE CIMEX LECTULARIUS, OR BED BUG.
Various are the antipathies of mankind, but all appear to unite in their dislike to this animal and the louse, and to detest them as their natural and nauseous enemies. The bug “intrudes upon the peace of mankind, and often banishes that sleep which even anxiety and sorrow permitted to approach: the night is the season when the bed bug issues from its retreat to make its depredations; by day it lurks in the most secret parts of the bed, takes the advantage of every chink and cranny to make a secure lodgement, and contrives its habitation with so much art, that scarce any industry can discover its retreat; but when darkness promises security, it then issues from every corner of the bed, drops from the tester, and crawls from behind the arras, and travels to the unhappy patient, who vainly wishes for rest and refreshment.”
Linnæus is of opinion that this insect is not originally of European growth, but was imported from some other country. It is not only disagreeable on account of the extremely offensive smell proceeding from it, but also because of the rapidity with which it increases, and the voraciousness of its appetite. It has two brown small prominent eyes, two antennæ, and a crooked proboscis, which lies close under the breast. Instead of wings, we find on the first ring of the belly two flat pieces which entirely cover it, and extend towards the sides. These plates, the trunk, and the head, are amply set with hairs. The proboscis is divided transversely into four parts, which are probably so many articulations; this piece is best seen on the under side of the bug, being bent flat on the belly, and reaching half way down the body; but the mechanism of this, as well as other parts of these minute insects, cannot be perfectly understood, but by an accurate examination with the microscope. It has six legs, each of which has three joints; these legs, like those of the fly, are formed for running, not leaping; the skin is shagreened, and the separation of the rings usually marked by a smooth shining band. On the belly, at a small distance from the edge, a set of circular spots may be perceived, two on each ring, except the last; these are the spiracula. Examined internally, we find one large artery, a stomach, and intestines. The instant it perceives the light, it endeavours to gain its obscure habitation, and seldom fails in making good its retreat.
OF THE PEDICULUS HUMANUS, OR LOUSE.
“Whenever wretchedness, disease, and hunger seize upon man, the louse seldom fails to add itself to the tribe, and to increase in proportion to the number of his calamities.”
When the human louse is examined with the microscope, its deformity fills us with disgust. In the head we may distinguish two fine black eyes, looking backward and fenced with hair; near these are the two antennæ, each of which has five joints set with short bristles; the fore-part of the head is rather long, the hinder more round or obtuse; there is a small part that projects from the nose or snout, this serves as a sheath or case to the proboscis or piercer, which the creature thrusts into the skin to draw out the blood and humours which are its destined food, for it has no mouth which opens in the common way.
This proboscis has been estimated to be seven-hundred times smaller than a hair; it is contained in another case within the first, and can be drawn in or thrust out at pleasure; the skin is hard and transparent. From the under side proceed six legs, each of which has five joints, and terminates in two unequal hooked claws, these it uses as we would a thumb and finger; there are hairs between the claws, as well as all over the legs; the body finishes in a cloven tail, which is generally covered, and partly concealed by hairs.
From the extreme transparency of its skin, the internal parts may be seen to greater advantage than in any other insect; as, the various ramifications of the veins and arteries, in which a kind of regular pulsation may be observed, as well as the peristaltic motion of the intestines, which is continued from the stomach to the tail. When the louse feeds, the blood rushes like a torrent into the stomach, moving with so strong a propulsion and contraction, as appears very curious. The digestive powers are so great, that the colour of the blood changes in its passage from thick and black at its first entrance, to a fine ruby colour in the intestines, and nearly white in the veins. Its greediness is so great, that the excrement contained in the intestines is ejected at the same time, to make room for this new supply. There is scarce any animal that multiplies so fast as this unwelcome intruder; the moment it is excluded from the egg it begins to breed.
It would be endless to describe the various creatures which go under the name of lice, and swarm upon every part of nature. The reader, desirous of a more particular account of those which infest various animals, will obtain full satisfaction, by consulting Rhedi’s Treatise de Generatione Insectorum.
OF THE ARANEA, OR SPIDER.
The spider is another insect which is often examined with the microscope, and certainly affords much matter for observation. “Formed for a life of rapacity, and incapable of living but by blood, all its habits are calculated to deceive and surprize; it spreads toils to entangle its prey; it is endued with patience to expect its coming, and is possessed of arms and strength to destroy it when fallen into the snare.”
“———— To heedless flies the window proves
A constant death; where, gloomily retired,
The villain spider lives, cunning and fierce,
Mixture abhorr’d; amid a mangled heap
Of carcases, in eager watch he sits,
O’erlooking all his waving snares around.
Near the dire cell the dreadless wanderer oft
Passes, as oft the ruffian shews his front;
The prey at last ensnar’d, he dreadful darts
With rapid glide along the leaning line;
And fixing in the wretch his cruel fangs,
Strikes backward grimly pleas’d: the flutt’ring wing
And shriller sound declare extreme distress,
And ask the helping hospitable hand.” Thomson.
The eyes of the spider have been described in [page 199], they are a very beautiful microscopic object, viewed either as transparent or opake. The spider has eight legs with three joints, thickly beset with hairs, and terminating in three crooked moveable claws, which have little teeth like a saw; at a small distance from these claws, but placed higher up, is another something like a cock’s spur, by the assistance of which it adheres to its webs; but the weapon wherewith it seizes and kills its prey is a pair of sharp crooked claws or forceps placed in the fore-part of the head. The insect can open or extend these pincers as occasion may require; when undisturbed, it suffers them to lie one upon another, concealed in two cases constructed for their reception. Leeuwenhoeck says, that each of these claws has a small aperture or slit, through which he supposes a poisonous juice is injected into the wound it makes.
The exuvia, or cast-off skin of the spider, which may be found in cobwebs, being transparent, is an excellent object; and the fangs or forceps may be more easily separated from it, and examined with greater exactness than in a living subject. The contexture of the spider’s web, and the manner of weaving it, have been discovered by the microscope. The spider is supplied with a large quantity of glutinous matter within its body, and five tubercles or nipples for spinning it into thread, of what size it pleases, either by opening or contracting the sphincter muscles. This substance, when examined accurately, will be found twisted into many coils, of an agate colour, and which from its tenacity may be easily drawn out into threads. The five nipples are placed near the extremity of the tail; from these the aforesaid substance proceeds; it adheres to any thing against which it is pressed, and being drawn out hardens in the air. The threads unite at a small distance from the body, so that those which appear to us so fine and single, are, notwithstanding, composed of five joined together, and these are many times doubled when the web is in formation. The web serves him for the double purpose of an habitation and of a machine for catching his food; for in the center of this web it dwells in dismal solitude, like a dragon in his lonely den, an image of the evil one, wasting all things round about it, and eager to destroy every appearance of life. When first hatched, even these loathsome insects seem endued with a principle of association, spinning a web in common; but this connection is of short duration, and soon terminates by their destroying one another. If, like the silk-worm, they were disposed to live together peaceably, it is possible that their labours might be productive of advantages nearly similar to that valuable insect; for which purpose repeated attempts have been made, though they proved ineffectual.
OF THE CULEX, OR GNAT.
The gnat is a beautiful object for the microscope. The curious manner in which it disposes its eggs upon the surface of the water has been noticed in [page 288]. From the egg proceeds the larva, in which state it is most happily suited to shew the several operations of life; for a moderate magnifying power will discover what passes within its transparent body. It has a large scaly head, with two large antennæ, besides several hairy parts, and articulated bristles near the mouth, which are in continual motion. If the worm be dissected, the feet of the gnat may be found folded up in the divisions of the thorax; the abdomen is divided into eight rings, from the edges of each of which three or four bristles proceed. The tail is divided into two parts of very different forms; by one of these it can steer itself in any direction; in the other, two pulmonary tubes may be discovered, through which the insect breathes. The larva has a power of moistening the tail with an oleaginous liquor, by which means it can suspend itself on the surface of the water. On agitating the water, the worms descend with precipitation to the bottom; but they soon return to the surface, to breathe the air through the tube that is annexed to their tail. From this state, they pass into that of the pupa, which is the gnat enclosed in a third skin, under which it is formed and strengthened; the organs of respiration are changed, breathing at this period through a couple of horns, which are placed near the head, keeping itself rolled upon the surface of the water, though on the least motion it unrolls itself and descends, aided by the oars near the tail.
From the spoils of the pupa, a little winged insect proceeds, whose every part is active to the highest degree, and whose entire structure is the just object of our admiration. Its head, adorned with feathers, is a fine microscopic object; but the proboscis may be deemed one of the most curious instruments in the insect creation. This formidable apparatus has been particularly described in [page 187].
The exuviæ or cast-off skins of insects, being exceedingly transparent, are well adapted for observation, as they exhibit the external appearance of the little animal; among these, may be reckoned those of spiders and cimices, but particularly the forficula auricularia or earwig, which is an elegant exuvia; a magnified view of the beautiful wing of this insect is exhibited in [Plate XIV.] and described in [page 205]. The stings of insects vary not only in their form, but also in their apparatus; most of them require dissection; as the stings, for they have generally two, are inclosed in a hard sheath or case, to which is added a pair of feelers. The stings of bees, wasps, &c. are barbed, while those of the chrysis are serrated, or notched like a saw. The head of insects is furnished with an instrument or proboscis various as the insects themselves, but all meriting attention, as being admirably adapted to their different uses and purposes. Among the most remarkable are those of the bed bug, flea, gnat, empis, conops, &c. to which may be added the singular one of the tabanus, described in [page 188], and figured in [Plate XVI.] A description of the apparatus of the bee has also been given in [page 181], and of that of the butterfly in [page 186].
The antennæ of moths, butterflies, and most other insects, display as great beauty in their formation as they are endless in their variety; the distinguishing characters of many of them have been described in [pages 190]-[193], and that of the lepas anatifera in particular in [page 345], and exhibited in [Plate XIII.]
The eyes of insects are singularly constructed, but this structure is not discoverable without the assistance of the microscope; the eyes of the libellula are hexagonal, see [Plate XVI.] Fig. 3, and their description in [page 195]; those of the lobster are square, as exhibited in Fig. 5 of the same plate, and described in [page 197].
The hair of animals, as the mouse, goat, large bee, and many species of caterpillars, particularly the tufts on the head and tail of the larva of the phalæna antiqua, offer many beauties to the curious observer. The bristles of a hog, cut transversely, appear tubular, and the root of hair is evidently bulbous.
The muscular fibres, and every anatomical preparation that can be brought under the microscope, are pleasing objects; the reader will meet with many curious and interesting observations on the hairs, the muscles, nerves, and other parts of the human body, in Fontana’s Treatise on the Venom of Vipers.
The legs of all insects appear very much diversified, and their mechanism truly astonishing, according with their different occupations, as particularized in [pages 210]-[212].
Scales of fish, as soles, roach, dace, salmon, eels, &c. as also the scales of snakes, lizards, &c. &c. Specimens of scales are given in [Plates X.] and [XIX]. The scales form a light, but at the same time a solid and smooth covering to the fish; they hinder the fluid from penetrating the body, for which purpose they are laid in a kind of natural oil; they serve also as a protection, and break the force of any accidental blow, which may be the reason why river-fish have larger and stronger scales than sea-fish, being more liable to accidents.
The purple tide of life, nay the very globules of the blood, may be seen distinctly rolling through veins and arteries smaller than the finest hair.[151]
[151] The manner of viewing the particles of the blood has been described in [p. 149], together with some remarks on their form, by our author. It was not my intention to have renewed the subject; but a chirurgical treatise having been lately published by Everard Home, Esq. F. R. S. in which it appears that he has paid particular attention towards investigating these minute particles, and ascertaining their true form, I shall here subjoin an abstract.
“As the result of microscopical experiments has been found exceedingly fallacious, a prejudice has very naturally arisen against all experiments of this kind upon the secretions of the human body, from a supposition that they are not to be depended upon. But it is right that we should discriminate, and not condemn the use of the microscope altogether, because from ignorance of its principles it has been misapplied; since these very deceptions have been the means of our acquiring a more accurate knowledge of the use and application of that instrument.
“The errors in the use of the microscope have arisen from increasing the magnifying powers of the glasses too much, and not taking in all the circumstances relating to the refraction of the rays of light, making no allowance for the aberration. An attention to the aberration alone will explain the different appearances under which the red globules of the blood have been represented. Some have found them perfect spheres, which will always be the case when the glasses are perfectly adjusted, and the object placed at the true focal distance. Others have found them annular, from the object being at the focal distance of the rays transmitted near the circumference of the magnifying glass, which are refracted in a greater degree, and consequently shorter than the central rays. Others, again, have viewed them as flattened bodies of a circular figure, bright in the center, and becoming darker towards the edges; which appearance arises from the object being at the focal distance of the central rays of the magnifying glass, which will be less refracted than those near the circumference. Although such are the errors which arise, when microscopical researches are pushed beyond certain bounds; yet, that the red part of the blood is made up of globules, is a discovery for which we are indebted to the microscope, and which seems to be as well ascertained as any discovery in anatomy or physiology. The appearances of pus are equally distinct, when examined on the field of a microscope, as the globules of the blood; they are visible with a small degree of magnifying power, and are the same to the eyes of different persons.” Edit.
Feathers, and parts of feathers of birds, are not to be passed by or unnoticed; but it is impossible to point out any of these in preference to others, as each has its peculiar beauties; the plumulæ of these have generally in the microscope the appearance of large feathers; the pith contained in the quill, if cut transversely and examined, exhibits an admirable reticular texture. Many other parts of birds will afford a great variety of curious objects, particularly the egg: Mr. Martin says, that the internal spongy substance of bones may be better observed in those of birds, than of any other animal; even the feathers or scales of a moth’s wing amply repay the observer; these also vary in their texture and figure; but the largest and most commonly applied, are from the body of the sphinx stellatarum, or humming-bird moth; a specimen is given in [Plate XVI.] Fig. E F H I.
Transverse sections of all kinds of wood, especially those of a pithy or soft nature, form some of the most delightful objects for the microscope; among these, the section of fern root will be found strikingly curious, from the singular disposition of the air and sap vessels; their beauty will be seen by the figures in [Plates XXVIII.] [XXIX.] and [XXX.]
Flowers, whose brilliancy and variety constitute one of the principal beauties of nature, each being distinguished from the rest by some peculiar beauty or shining character.
The flowers of most grasses, with all the varieties of mosses; the farina of flowers; mouldiness, which evidently appears to vegetate; all the kinds of sponge; sea-weeds; particularly the confervæ, which are jointed like a cane. The extensive family of corallines present an elegant appearance; the most beautiful are the sea hair, sea fir, sickle, fox tail, &c. described by Ellis.
Dissected leaves, which shew the fibres and nerves; the human intestine injected with wax is a fine object; as are many other anatomical preparations. The seed of the silver-rind birch appears like an insect; seed of the quaking grass is also much admired, as is the leaf which covers the seed of sorrel. Among artificial productions, the edge of a razor, and point of a fine needle, as also fine cambrick, evidently discover the inferiority of the workman; particles from the collision of flint and steel; wire melted by the electric explosion, and other articles innumerable.
Besides these, there is an immense variety of objects which can only be satisfactorily examined alive, such as polypes, minute aquatic insects; animalcula of various infusions, as eels in paste, vinegar, &c. The eyes and teeth of snails; the circulation of the blood in the tails of fishes, &c.[152]
[152] Those who possess leisure, particularly such who reside in the country, may easily procure the major part of the preceding objects, and also add an extensive variety to them; but those who have not the opportunity of collecting for themselves, may be supplied with objects in considerable variety by application to Messrs. Jones. Edit.
CHAP. XI.
AN ARRANGEMENT AND DESCRIPTION OF MINUTE AND RARE SHELLS.—A DESCRIPTIVE LIST OF A VARIETY OF VEGETABLE SEEDS, AS THEY APPEAR WHEN VIEWED BY THE MICROSCOPE. BY THE EDITOR.
Notwithstanding the abundance of objects which have from time to time afforded delight to the attentive and diligent microscopic observer, little doubt can be entertained but that amidst the immense variety of minute shells, as well as the seeds of vegetables, numbers remain unexplored, though highly meriting notice.
With the hope of exciting the attention of the curious toward these subjects, and affording hints to those who may happily possess inclination, together with leisure and opportunity to pursue the inquiry, I shall enumerate to the reader a few specimens of each of these admirable productions of nature; towards the elucidating of which, very little, comparatively, has as yet been done.
As far as my knowledge extends, the first author who has treated on the subject of minute and rare shells, is Plancus, who published a treatise in quarto, at Venice, in the year 1739, with the title “De Conchis Ariminensibus minus notis;” a third and improved edition of which appeared in 1760. It is a very curious and learned work, containing a natural history of testaceous animals of Rimini, an Italian town situated on the Adriatic shore; and more particularly of minute nautili.
In the year 1784, Mr. Walker of Faversham published in quarto a collection of minute shells, which was the joint production of himself and William Boys, Esq. F. S. A. of Sandwich, in Kent, assisted by the late Edward Jacob, Esq. F. S. A. It contains an arrangement and concise description of ninety shells, accompanied with neatly engraved figures of the whole series; the greater part of them as well in their magnified state, as that in which they appear to the naked eye. Specimens of those which are esteemed most curious and rare, I have selected from this work: a reference to the original will afford the reader more complete satisfaction, and possibly animate him to further pursuits.
This publication appeared in so favourable a light to that eminent patron of science, Sir Joseph Banks, that I should accuse myself of unjustifiable remissness, were I to neglect this opportunity of introducing an extract from the copy of a letter addressed by him to the late Mr. Jacob, which is now in my possession.
“We” (the Royal Society) “are all much obliged to you for the pains you have taken in bringing this work to light. Natural history is, I am convinced, more benefited by a thin volume of real new facts, which is the case in yours, than by a folio of comments generally written by those who mean to receive praise, more founded on the elegance with which they express the ideas they conceive, than on any prospect of utility to be derived from the ideas themselves. From such naturalists, De Buffon, &c. good Lord deliver our honest science.”
That truly amiable, and no less intelligent lady, the late Duchess Dowager of Portland, likewise expressed her approbation of the work in a letter to Mr. Boys.
By this publication, a number of shells, heretofore unknown, are added to the British conchology, sufficient to shew that the path is now laid open and made easy of access to inquisitive naturalists in different parts of the kingdom for still greater discoveries. Indeed, it is rather extraordinary, that the authors of this country, who have so advantageously applied the microscope to a variety of objects in the animal kingdom, should have neglected to examine the shores of our own seas, crowded as they are with objects equally worthy of their investigation. Baker’s observation in his “Employment for the Microscope,” p. 244, is entitled to more attention than has been paid to it. “Shell-fish,” says he, “are objects that have as yet been very slightly examined by the microscope, and therefore the serious inquirer into nature’s secret operations may here be certain of discovering beauties, which at present he can have no conception of.” But thus it is, nature opens her rich and inexhaustible treasures by slow degrees to the inquisitive mind of man. In fact, different observers have generally different pursuits, otherwise these objects would scarcely have escaped the attention of many ingenious naturalists, particularly the quick-sighted Mr. Ellis, who has so clearly investigated and described the corals and corallines of the adjacent coasts.
To those who have perused the treatise of Plancus, already mentioned, it is necessary to observe, that though the sand on our coasts contain a vast variety of specimens, yet it by no means appears so productive as the sand of Rimini; lest, despairing of success in their first researches, they may be induced to desist from further examination. Every parcel will, however, be found to contain some of the more common shells.
It may not be improper here to point out to future inquirers the mode of facilitating the discovery of these minute objects. The sand being perfectly dried, put a handful on an open sheet of paper, and by gently shaking it from side to side, the minute shells, being specifically lighter than the sand, will be separated from, and lie on its surface, and will thus be more expeditiously procured than by any other method. It is also adviseable to place the objects intended for inspection in a situation secured from any sudden blast of air, otherwise, owing to their levity, they may be unexpectedly blown away, and a loss sustained of some of the rarer specimens; even incautiously breathing on them, or coughing, may be productive of similar disagreeable effects.
The following observations by an ingenious critic[153] are so apposite, and so perfectly coincident with my own sentiments on the subject, that I cannot resist the impulse I feel to enable the reader to partake of the pleasure which I have experienced in their perusal.
[153] Monthly Review, Vol. LXXI. p. 190.
“Let not the minuteness of the objects here delineated call up the surly inquiries of those, who have not been accustomed to live with their eyes open to the works of nature: they are not fit judges in these matters. If they will persist in asking, Of what use is all this labour? What good can accrue to mankind from this knowledge, in point of food, or other use? We know of none at all, either present or likely to happen, as to the body, for use or ornament, or to the satisfying any appetite: nevertheless, a much nobler idea will take its rise in our opinion; one which, by displaying so momentously the power of the omniscient Creator, will thwart the infidel in his favourite ideas of escaping the eyes of the Almighty, and force him, as he descends the scale from the more immense objects to these minutissima, to confess, that the being which has formed these, can fully equal all that the tongue of man has yet declared of the possibility of his power. For, what a train of wonders have we here to pursue? What must be the œconomy of animals so very diminutive, so weak, so exposed from their situation to the force of every rude wave, and who, notwithstanding, so often escape unhurt? How do they rear their young? From whence collect their prey?”
A DESCRIPTION AND ARRANGEMENT OF MINUTE AND RARE SHELLS.[154]
[154] Being possessed of Mr. Jacob’s own corrected copy of the work, to which he has annexed the trivial names, I am thereby enabled to affix them to the several shells here enumerated.
SERPULA.
THE WORM-SHELL.
Serpula Bicornis.
[Plate XIV.] Fig. 2. S. bicornis ventricosa. The bellied semilunar worm-shell.
The colour white, opake, and glossy. From Sandwich and Reculver, though not common.
Serpula Perforata.
Fig. 3. S. bicornis umbilico perforato. The semilunar perforated worm-shell.
The colour white, opake, and glossy. From Sandwich: very rare.
Serpula Lactea.
Fig. 4. S. tenuis ovalis lævis. The thin, smooth, egg-shaped worm-shell.
The colour pellucid, with milky veins. From Sandwich: not common.
Serpula Lagena Sulcata.
Fig. 5. S. (lagena) striata sulcata rotunda. The round striated and furrowed flask worm-shell.
The colour whitish, transparent, and glossy. From Sandwich, Reculver, and Shepey: very rare.
Serpula Retorta.
Fig. 6. S. (retorta) rotunda marginata cervice curvatim exerto. The marginated retort worm-shell.
The colour white and opake. From Sandwich: not common.
Serpula Incurvata.
Fig. 7. S. recta anfractibus tribus contiguis regulariter involutis. The straight horn worm-shell, with three close intorted spires at the tip.
The colour white, semitransparent. From Sandwich: rare.
This shell, though resembling the semilituus of Linnæus, p. 1163, [No. 280], is not of the genus of Nautilus, having neither syphon in the aperture, nor the internal concamerated structure.
DENTALE.
THE TOOTH-SHELL.
Dentalium Imperforatum.
Fig. 8. D. apice imperforata transverse striatum. The imperforated transversely striated tooth-shell.
The colour white and opake. From Sandwich: not very common.
PATELLA.
THE LIMPET.
Patella Rota.
Fig. 9. P. plana orbiculata margine regulariter dentato. The toothed-wheel limpet.
The colour white and opake. From Sandwich: extremely rare.
HELIX.
THE DEPRESSED SNAIL.
Helix Carinata.
Fig. 10. H. striata apertura compressa tribus anfractibus carinata. The striated suboval-mouthed snail, of three spires and a sharp edge.
The colour light brown pellucid. In a fresh water stream, near Faversham.
Helix Spinosa.
Fig. 11. H. subglobosa umbilicata ore subrotundo margine spinoso. The roundish mouth deeply umbelicated snail with a thorny margin.
The colour brown pellucid. From Bysing Wood, near Faversham: exceeding rare.
Helix Reticulata.
Fig. 12. H. unici anfractus subumbilicata apertura rotunda marginata eleganter reticulata. The round mouthed reticulated single spired slightly subumbilicated snail.
The colour white and pellucid. From Reculver: extremely rare.
Helix Striata.
Fig. 13. H. striata apertura subovali anfractibus supradorsalibus. The oval mouthed striated snail with the spires reflected on the back.
The colour greenish, white pellucid. From Sandwich: very rare.
TURBO.
THE PRODUCED SNAIL.
Turbo Reticulatus.
Fig. 14. T. subumbilicatus quatuor anfractibus reticulatis apertura subrotunda. The slightly umbilicated turbo with four reticulated spires, and a roundish aperture.
The colour white and pellucid. From Seasalter: very rare.
Turbo Eburneus.
Fig. 15. T. quinque anfractibus ventricosis apertura subrotunda. The five spired ventricose turbo with a roundish mouth.
The colour white and opake. From Reculver: very rare.
Turbo Strigatus.
Fig. 16. T. tribus anfractibus primo strigis tribus transversis apertura subovata. The three spired turbo, the first spire with three transverse ridges and a suboval aperture.
The colour opake white. From Seasalter: very rare.
Turbo Albidus.
Fig. 17. T. turritus septem anfractibus strigatis apertura ovali. The taper turbo with seven ridged spires and an oval aperture.
The colour opake white. From Sandwich: rare.
Turbo Carinatulus.
Fig. 18. T. turritus carinatus septem anfractibus apertura coarctata marginata. The taper carinated turbo with seven spires and a contracted marginated aperture.
The colour opake white. From Sandwich: very rare.
Turbo Clathratulus.
Fig. 19. T. clathratus sex anfractibus apertura ovali marginata. The barred six spired turbo with an oval marginated aperture.
The colour opake white. From Sandwich: exceeding rare.
Turbo Crassus.
Fig. 20. T. crassus clathratus quinque anfractibus apertura rotunda marginata. The thick barred turbo of five spires and a round marginated aperture.
The colour opake white. From Sandwich: very rare.
Turbo Punctatus.
Fig. 21. T. turritus perversus novem anfractibus punctatis apertura coarctata. The reversed taper turbo of nine dotted spires and straitened aperture.
The colour light-brown opake. From Sandwich: not common.
Turbo Shepeianus.
Fig. 22. T. sex anfractibus reticulatis apertura ovali submarginata. The six spired reticulated turbo with an oval submarginated aperture.
The colour semipellucid white. From Shepey island: very rare.
Turbo Sandvicensis.
Fig. 23. T. tribus anfractibus reticulatis apertura unidentata. The three spired elegantly reticulated turbo with a one toothed oval aperture.
The colour pellucid white. From Sandwich: exceeding rare.
TROCHUS.
THE TOP-SHELL.
Trochus Fuscus.
Fig. 24. T. umbilicatus quinque anfractibus marginatus apertura subrotunda. The five spired umbilicated marginated top-shell with a roundish aperture.
The colour opake brown. From Sandwich: common.
BUCCINUM.
THE WHILK.
Buccinum Obtusulum.
Fig. 25. B. ampullaceum tribus anfractibus apertura ovali. The bellied whilk of three spires with an oval aperture.
The colour opake white. From Faversham Creek: very rare.
Buccinum Longiusculum.
Fig. 26. B. turritum quinque anfractibus apertura ovali. The taper whilk of five spires with an oval aperture.
The colour white semipellucid and glossy. In Faversham Creek only; but not uncommon there.
VOLUTA.
THE VOLUTE.
Voluta Alba.
Fig. 27. V. alba opaca longitudinaliter striata. The white opake volute. From Sandwich and Shepey island: not uncommon.
This shell resembles Mr. Pennant’s voluta Jonensis, but differs in the form of the aperture, as well as in the size.
BULLA.
THE DIPPER.
Bulla Regulbiensis.
Fig. 28. B. crassa apertura medio coarctata. The thick dipper, with a compressed aperture.
The colour white and opake. From Reculver: very rare.
NAUTILUS.
THE CHAMBERED NAUTILUS.
Nautilus Beccarii.
Fig. 29. N. spiralis umbilicatus geniculis insculptis. The spiral umbilicated nautilus with deep joints.
The colour, while the fish is alive, is a fine pellucid crimson; when dead, is white. It is found alive on the fucus vesiculosus, and is a very common shell on all the coast, and seems to be an universal litoral one, by the numbers found at Rimini, and in the sand of the South Seas.
Lin. S. N. p. 1162, No. 276. Nautilus Beccarii. Planch. Tab. 1. Fig. 1. Gualtier, Tab. 19. Fig. H, H, I.
Nautilus Crispus.
Fig. 30. N. spiralis geniculis crenatis. The spiral nautilus with crenated joints.
The colour opake white. The finest specimens are from Shepey: not uncommon.
Lin. S. N. p. 1162, No. 275. crispus. Planch. T. 1. f. 2. Gualt. T. 19. f. A. D.
Nautilus Calcar.
Fig. 31. N. spiralis apertura lineari geniculis elevatis. The spiral nautilus, with a narrow aperture and raised joints.
The colour opake white. From Shepey island: not common.
Lin. S. N. 1162, No. 274, calcar. Pl. T. 1. f. 3, 4. Gualt. T. 19. f. C. B.
Nautilus Lævigatulus.
Fig. 32. N. spiralis geniculis lævibus. The spiral nautilus with smooth joints.
The colour semipellucid, white and glossy. From Sandwich and Seasalter: not common.
Nautilus Depressulus.
Fig. 33. N. spiralis utrinque subumbilicatus geniculis depressis plurimis. The spiral subumbilicated nautilus, with many depressed joints.
The colour opake white. From Reculver: very rare.
Nautilus Umbilicatulus.
Fig. 34. N. spiralis umbilicatus geniculis sulcatis. The umbilicated spiral nautilus, with furrowed joints.
The colour opake white. From Sandwich: not common.
Nautilus Crassulus.
Fig. 35. N. spiralis crassus utrinque umbilicatus geniculis lineatis. The thick spiral doubly umbilicated nautilus, with fine joints.
The colour opake white. From Reculver: exceeding rare.
Nautilus Lobatulus.
Fig. 36. N. spiralis lobatus anfractibus supra rotundatis subtus depressioribus. The spiral lobated nautilus, with the spires rounded on the upper side, and depressed on the under.
The colour opake white. From Whitstable: not common.
Nautilus Carinatulus.
Fig. 37. N. oblongus carinatus apertura lineari ovali. The oblong carinated nautilus, with a narrow oval aperture.
The colour whitish, transparent like glass. From Seasalter and Sandwich: very rare.
Nautilus Subarcuatulus.
Fig. 38. N. subarcuatus geniculis exertis. The bending nautilus with raised joints.
The colour opake brown. From Shepey island: very rare.
MYTILUS.
THE MUSCLE.
Mytilus Phaseolus.
Fig. 39. M. lævis valvulis antice inflexis. The smooth muscle, with the valves inflected in front.
The colour brown and glossy. From a fresh water stream near Faversham: common.
Mytilus Punctatulus.
Fig. 40. M. subrhombiformis punctatus. The subrombic dotted muscle.
The colour pellucid white. From Sandwich: common.
Mytilus Discors.
Fig. 41. M. discors areis tribus distinctis. The divided muscle.
The colour opake brown. From Sandwich: not common.
Lin. S. N. 1159, No. 261. Da Costa Br. Conch, p. 221. Tab. 17. f. 1. where it is exactly described, and as badly engraved.
ANOMIA.
THE SCALE.
Anomia Squamula.
Fig.42. A. squamula. The scale anomia.
The colour opake white and glossy. From Sandwich: not uncommon.
Lin. S. N. 1151, No. 221. This shell is well described by Da Costa; but neither he, or Mr. Pennant, have caused it to be engraved.
ARCA.
THE ARC.
Arca Modiolus.
Fig. 43. A. oblonga striata antice angulata. The oblong striated arc, with the foreside angulated.
The colour opake white. From Sandwich: not uncommon.
Lin. S. N. p. 1141, No. 171. Arca Modiolus.
CARDIUM.
THE COCKLE.
Cardium Muricatulum.
Fig. 44. C. subcordatum antice muricatum. The heart cockle, with the front muricated.
The colour opake white. From Shepey island: not uncommon.
LEPAS.
THE ACORN-SHELL.
Lepas Strigatulus.
Fig. 45. L. balanus striatus apertura obliqua. The striated acorn-shell, with an oblique aperture.
The colour light brown. From Sandwich, on the roots of sea-weeds, the finest specimens on lobsters: not uncommon.
ECHINUS.
THE SEA-URCHIN.
Echinus Lobatulus.
Fig. 46. E. subrotundus planus lobatus. The flat roundish lobated echinus.
The colour opake white. From Reculver: rare.
ASTERIAS.
THE STAR-FISH.
Asterias Triradiata.
Fig. 47. A. triradiata lævis. The smooth three-rayed star-fish.
The colour white, transparent as glass. On all the different shores that have been examined.
Having thus described a few specimens of those pleasing microscopical objects, minute shells, I shall agreeably to the intimation given in the [note] to [page 613], proceed to
A DESCRIPTIVE LIST OF A VARIETY OF VEGETABLE SEEDS.[155]
[155] To the names as given by Dr. Parsons, those adopted by Linnæus are here added.
Lithospermum Officinale.
[Plate XV.] Fig. 1. Ibid. Linn. Gromwell. This seed is in figure exactly like a human heart without the auricles, but has no flat or depressed part on its sides; it is pretty circular round its thickest part, and terminates in a blunt cone. At the thickest extremity there is a circular roughness, which is the umbilicus, and from thence to the cone on the shortest side it is bisulcated longitudinally; so that the space between the sulci is a kind of ridge, nor do either sulci or ridge extend to either extremity of the seed; the rest of the surface is smooth and polished, the ground a light ash-colour, with a shade or cloud of yellow or brown.
These seeds are very hard, and the ash-coloured shell is brittle like that of a hen’s egg; which being broken, appears to be lined with a light olive-coloured uniform membrane, which encloses a nucleus of a Spanish snuff-colour, pretty smooth, and of the same form with its shell, being in close contact with it all round.
The natural size of a middling grain of this seed is about the eighth part of an inch long, and the ninth of an inch in diameter at the roundest part.
Cyminum.
Fig. 2. Cuminum C. Linn. Cummin. This seed is double, though fixed side by side to one little stem; both which while together seem like one, and are ribbed in an uneven manner longitudinally, having great numbers of little threads or fibres sticking out all over them, which makes them look hoary. They are thick in the middle and run to a cone at each end. At the upper extremity there is an appearance like a bifurcation in the stilus, each of them belonging to its particular seed; this appears when the seeds are separated.
These seeds are of a darkish straw-colour, the little threads or fibres being much lighter than the body of the seed. Each of these seeds contains in it a kernel of an olive-colour, and exactly in shape like a waterman’s boat, and of the same proportion, having a concave and convex side; the latter has a blunt ridge like the keel of a boat, and the former has a white line from one end to the other, which proves to be a ridge, to which the stilus that rises from the little stem of the seed, adheres to support it.
When the seeds are together upon the stem their length is about the fifth part of an inch, and about an eighth part of an inch in the broadest part.
Papaver Album.
Fig. 3. P. somniferum. Linn. Poppy. This is a little yellowish white seed exactly resembling in shape a sheep’s kidney, having a yellow place about the hollow part, which is its umbilicus, analogous to the hollow part of the kidney into which the blood-vessels (emulgents) enter.
If it be viewed on the back or convex part, concealing the hollow, it is exactly shaped like an egg, having one end somewhat rounder than the other.
All over its surface it has superficial cells, formed by ridges that rise from the surface, which are some heptagons, some pentagons, but for the most part hexagons, though not precisely of equal sides; and the bottoms of these cells seem to be very porous.
The seeds seem very light and springy, as a gentle blast of ones breath is capable of blowing them away, or a touch of any thing of making them roll a considerable way. As to their size, they are not above a twenty-fourth part of an inch long, and about a thirtieth part broad or thick.
Carduus Benedictus.
Fig. 4. Centaurea Benedicta. Linn. Blessed Thistle. The body of this seed is about twice as long as it is thick, is round and shaped much like a nine-pin, only instead of being small at the upper end, it has a stricture, from whence arises a beautiful crown of ten angles or points, out of which come also ten aristæ or spiculæ like ivory, about the length of the body of the seed, running taper upward, and set round in an uniform manner. Within the circle of these long spikes there are ten more, which are but very short, and of the same colour and consistence with the others. When these are all plucked off, the vestiges of the circles they form appear in the upper surface of the crown; in the middle of which a little process arises, but very superficially. That part which appears circular is white, and the rest of this surface, of the corona, of the same colour with the rest of the body of the seed, which is a sort of an olive-colour.
The body of the seed is of the sulcated kind, and looks exactly like a fluted pillar, and the surface shines as if varnished with some gummy substance.
At the lower or small end of this seed, there is an opening reaching up above a third of the length of the body of the seed, which discovers a white root, shaped like a cone at the bottom, and rising thicker by degrees till it divides into three limbs; these run taper upwards, till they are lost in the parenchyma of the seed, which at the place of their entrance appears somewhat fungous, but is more compact and clammy through its substance.
The length of the body is more than two eighths of an inch, and the aristæ exactly the same length. The corona is its umbilicus.
Plantago.
Fig. 5. P. Major. Linn. Plantain. By the imperfect idea we have of this seed from its minuteness, it may seem like a flea, as any small speck would, if a little oblong; yet its form is not constant, that is, there are scarce two of them precisely alike, some being perfectly elliptical, some with blunt angles, and some approaching a spheroid. They have a whitish mark on one side, which is the umbilicus of the seed, from whence the first rudiments of the plant spring, and the surface is entirely granulated over, and has a general appearance like some kinds of plumb-stones; the surface also shines a little, as if oiled or moist, and their colour is brown. One of the seeds cut transversely appears to have the shell or covering pretty strong in proportion to its size, which contains a parenchyma that is very porous and succulent. It is about a sixteenth part of an inch long, and a twenty-second broad.
Staphis Agria.
Fig. 6 and 7. Delphinum S. A. Linn. Stavesacre. The seeds of this plant are rough and angular, inclining to a triangle, although imperfectly so. They may be considered as having a basis or apex; the basis is thick and clumsy, and the apex runs to an angular point, which point is the umbilicus of the seed, out of which its first rudiments arise; it also has a convex and a plane or concave side; the former, Fig. 7, is rough, by reason of its being covered all over with porous cells, the ridges of which are also depressed or indented with rough pores, and granulated as if stuck full of sand. The concave surface, Fig. 6, is also rough, but not in the same manner, and so are the sides, which have a little flatness; these also are porous and sandy, and before the microscope, shine, and are coloured like dirty brown sugar-candy. The concave surface, notwithstanding the roughness, has one longitudinal ridge, and sometimes more, running from the basis to the apex, which has the same granulated surface with the rest. It contains a parenchyma, which is of a yellowish grey colour, and is moist and succulent.
This seed is in its natural size about two eighths of an inch long from its basis to the apex, and near as broad; however, some are broader in proportion to their length than others, and they are one eighth of an inch thick.
Anisum.
Fig. 8 and 9. Pimpinella A. Linn. Anise. Two of these seeds grow together upon one little stalk; when they are pulled asunder, they appear to have a flat and a convex surface. On the convex surface, Fig. 8, each seed has three ribs placed at equal distances from one another, which are porous and a little rough, being of a straw-colour; and the spaces between them are also rough and porous, but of an olive-colour. The flat surface, Fig. 9, has a white ridge running longitudinally from its basis to the apex in the middle; this white ridge or line serves to cling to the stilus, upon which it sticks. The stilus is also white, and has the same contexture with the ridge, and is bifid, in order to support two seeds with their flat sides together, which keeps them the more compact and less liable to injuries than if a single seed stuck on. It is certain, a single stilus would do as well to support two seeds as the bifid one, for even the two stick together as if single, if there was not a necessity for a double stilus, for a very important reason; which is, that when the seeds are ripe, they would stick on a single one, till the time of their being scattered about would pass, which would be a detriment to their propagation; but the stilus being double, and of a springy nature, the two parts are glued together, as long as moisture remains about the seeds capable of keeping them together; but when the seeds are grown ripe and dry, then this moisture is exhaled, and the stilus, as well as the flat surfaces of the seeds, begin to contract from their former plumpness; the stilus first begins to split asunder, and thereby separates the two surfaces of the seeds, each of which sticks loosely to its particular limb of the stilus; till at length the remaining moisture exhaling more and more, it grows rigid, and cracks with a blast of wind, and so the seed is scattered or sown in the ground in its due time. This is a most excellent provision of nature, and highly worth regard.
When the two seeds are sticking together, they have a round end which is the basis, and grow smaller by degrees upward, till they become an apex, having upon each seed a kind of fungous or bulbous corona, which is the umbilicus of the seed; and the shape of the two together may be compared to that of a given fig reversed. The parenchyma of these seeds is that of a pale greenish olive-colour. They are more exactly of a size than most other seeds, and are each one-eighth part of an inch long, and more than half that breadth.
Fœniculum Dulce.
Fig. 10 and 11. Anethum F. Linn. Sweet Fennel. In viewing these seeds, they do not look much unlike one species of the cucumber in general, some of them being thicker and longer than others, and some straighter; but upon applying the microscope, the ridges appear high, and form deep furrows.
Two of these seeds grow together upon the same little stalk, which is divided, like that of the anise seed, into a double or bifid stilus, in the same manner, and for the same reasons; when the two are pulled asunder, they appear to have a flat surface, Fig. 10, and a round and ridged one, Fig. 11. On the former, these characters are conspicuous: viz. 1. The whitish cortex or covering of the seed shews its edge distinctly. 2. Withinside this edge a white fungous substance appears running parallel to, and in close contact with it, on each side from end to end, being both together about one-third of the breadth of the seed; and between these, in the center, there appears a dark brown elliptical substance, which, upon separating the cortical and fungous coverings, appears to be a nucleus, whose internal substance is of an olive colour and something succulent. On the external surface there appears three high ridges, and when the flat faces of the seeds are close together upon the stilus, so as to seem but one, these three ridges on each seed and the two edges of each meeting firmly together, form eight regular ridges equally divided upon that round body that we have before said to resemble a cucumber. The extremity which is fixed to the stem is smaller than the other; the latter has a fungous kind of process arising from the body of the seed, which is the umbilicus of the seed. The ridges are of a light straw-colour, and the bottoms of the sulci they form are darkish. A middling seed is somewhat more than two-eighths of an inch long, and above half that breadth.
Grana Paradisi.
Fig. 12 and 13. Amomum G. P. Linn. Grains of Paradise. These seeds are of an irregular form, but may be said to have a basis and apex; the basis is generally so flat as to render it capable of standing well upon it; the sides consist of several flats and angles, and the apex looks very much like the mouth of a purse drawn or gathered up close together.
The body of the seed is of a reddish brown colour, the surface much granulated and rough; and the apex, which is its umbilicus, degenerates from this reddish brown colour into a yellow, appearing in little oblong ridges or plates.
Upon making a transverse section of this seed, a most beautiful appearance presents itself; the external cortex is very thin, and retains the same colour through its substance with the outer surface; this incloses a black, porous, pitchy substance, which is much thicker than the cortex, in close contact with it, and at the angles of the seed is pretty considerable. Next to this the parenchyma appears, as white as the finest white salt, and radiated from the center outward; and in this transverse section seems to have a round hole in the center of one of the divided parts, and a process answerable to it in the other. If a longitudinal incision be made through the middle, the appearance will be as in Fig. 13, when the center of the white parenchyma appears exactly like a modern vinegar glass, commonly called a cruet, the bottom of which tends obliquely towards the basis, and the top towards the apex of the seed. The surface of this part looks polished, and the colour is a yellowish olive; nor does it look unlike a gummy or resinous body; however, we cannot be certain what its substance is, notwithstanding its great resemblance to that kind of matter. The white parenchyma is very singular, being almost divided into two lobes by this little cruet, whose top runs up into or is lost in a remarkable circular part, which has a rising towards the umbilicus of the seed in form of an acorn, and this rising stands in the open place, into which the pursy umbilicus leads. As to its natural dimensions, an ordinary seed is somewhat more than the eighth of an inch long, and about an eighth thick.
Petroselinum.
Fig. 14. Apium P. Linn. Common Parsley. The seeds of this garden parsley, being of the umbellated kind, grow two upon a little stem, whose bifid stilus supports them like the ammi or smallage; they are striated or ribbed like those, having three of such ribs on the convex part, spread further asunder, and being much more conspicuous than those of either of the seeds just mentioned. There is another rib which runs on each side of the seed, which is its lateral rib, and that which runs round the edge of the flat surface makes it resemble the edge or gunnel of a barge or lighter, to which each of these bears some resemblance. This seed is considerably larger than either, and much longer in proportion to their size; the colour of the interstices between the ribs is a dusky olive, and the ribs of an oaker yellow. They are pretty round where they rest on the stem, and run up elliptically to an apex, where there is a fungous corona, which is the umbilicus. In making a transverse section through the middle of one of them, the parenchyma appears of the same form with the cortex, having this remarkable property, that between the ridges or ribs are canals, formed of the cortex and the surface of the parenchyma, containing a brown balsamic fluid, with which they are filled from one end to the other of the seed; and in some seeds this balsam appears all round between the parenchyma and the cortex. This will be further explained when we come to speak of the seseli, in which this is so apparent, that a transverse view of that seed will serve for both. The parenchyma is somewhat succulent, and of a greyish olive colour. An ordinary seed is one-eighth of an inch long, and about a sixteenth thick.
Petroselinum Macedonicum.
Fig. 15 and 16. Bubon Macedonicum. Linn. Macedonian Parsley. These are long slender elliptical seeds, growing like the seeds of other umbelliferous plants, two together on the stem and bifid stilus; when they are pulled asunder they appear each to have a convex or back side, and a flat part or belly. The convex side, Fig. 15, may be said, from its roundness at one end, and smallness at the other, to have a basis and apex; the former is round, and after swelling a little towards the middle, runs taper upwards, till within one-fifth of its length there arise two rough hairy processes, one on each side, like ears, and the rest runs to a point; so that the entire back surface is a near representation of a mouse lying flat. The colour of the body of this seed is a kind of olive, but the hoary fibres all over are of an ash-colour, and the striæ or ridges much the same.
The flat surface, Fig. 16, is of a brown colour and porous, having none of these fibres upon it; and is surrounded by an edge or ridge, like those on the back of the seed, which are also hoary. Upon this surface the bifid stilus is apparent, one extremity of which terminates at a hollow part, that may be likened to the under jaw of the mouse, between the roots of the ears; and the other stands loose, to which the fellow-seed was also attached.
The ridges are also hollow, like those of the garden parsley, and contain such a balsamic fluid as that; but this being so exceedingly slender, requires the greatest magnifier of the microscope for opake objects to discern it. This seed is about an eighth of an inch long, and about a twentieth broad.
Coriandrum.
Fig. 17, 18, and 19. C. sativum. Linn. Coriander. The seed of common coriander is spherical when entire, and may be said to have two poles; the lower, or that into which the stem is fixed, which forms a fungous hole, and the upper or little apex, as at Fig. 17, this is the umbilicus of the seed. From one of these poles to the other several ridges or striæ run like the lines of longitude upon the globe, between which there are several roughnesses; they are of a yellowish oaker colour, and about the sixth of an inch in diameter, or something less.
Each of these seeds, upon being bruised, divides into two hemispheres, Fig. 18, which discovers the edges of the rigid cortex, on the concave side there is a rising, and within it a lens, concave on one side and convex on the other, Fig. 19, as it is turned out of the cortex. On the concave side is a rising in the middle extending from one pole to the other, and on each side just below the apex, there is a white roundish fungous spot rising from the surface, from each of which runs downward a little curved a ridge, which appears to be resinous; and the surface is rough, and has a great many particles of resin also.
Seseli.
Fig. 20 to 24. S. Montanum. Linn. Long-leaved Meadow-saxifrage. This seed stripped of its foliaceous wings may be compared to a sort of canoo which is too narrow in proportion to its great length, has a hollow and a convex side, like that kind of boat, and is ridged longitudinally on its convex side, Fig. 20, from end to end, with four principal ridges; and between these, with others less considerable. There are, however, some of these seeds wider than others in proportion, but the majority are too long for their breadth, as I have said before.
These principal ridges are the support of the wings, and may be called their basis, for they rise broad from the body of the seed, and run out to a thin edge, which being continued constitute this leafy border. These are yellowish, and the spaces between them and the other less considerable ridges inclining to a brown.
On the concave side, Fig. 21, there is an edge or gunnel like that of a boat, and a considerable cavity from the edge; in the center of which the vestige of the stilus, Fig. 22, which is also bifid here, appears from one end to the other. The edge and this vestige are also of a yellowish colour, but the rest of the surface brown and porous, and the whole body of the seed and ridges shine, as if varnished over with some oily substance.
Fig. 23 is a view of the convex side of a seed divested of its wings, which is one of the most proportioned seeds I could pick out; at the upper extremity of which a little process may be perceived to turn or crook back upon the body; the same may also be discerned on that of Fig. 20. At the root of this process the opening or umbilicus of the seed lies.
Among the many beauties with which this seed abounds, there is one that is most agreeably surprising, which (says our author) I discovered by making a transverse section of one of them, in order to see what its internal substance consisted of. I no sooner applied the cut surface, Fig. 24, to my microscope, than each of the principal ridges, which I said above is the basis of the leafy wing, appeared to be a triangular tube, containing a fine brown liquid balsam of the colour of brown basilicon. This was a high entertainment, as every other curious discovery that arises by the diligent inspection of the seed is, and prompted my examining others in the same manner; and I found such a balsam as this common to the several kinds of parsley seeds also, as well as to that of the bishop’s weed and smallage; although these are so minute, that I could not be sensible of it but with difficulty, and with one of my greatest magnifiers. There is also something analogous to this in the sweet fennel and finoki, not in tubes of the husks or cortex, but rather in spungy channels that sink into the surface of the parenchyma, between the ridges of these last. The length of an ordinary seed is one-third of an inch, the thickness about an eighth, and the breadth of each wing nearly equal to the thickness of the body.
Hyoscyamus.
Fig. 25. H. Niger. Linn. Common Henbane. After the calyx has split and cracked by drying, the seed-pot comes to be exposed to the heat of the sun, which also grows dry, by which the lid or cover becomes loose, having no other visible attachment to keep it on the edge of the pot but its moisture, which in some measure helps to keep it there by agglutination, as well as by the squeezing or pressure of the segments of the calyx. But, this moisture exhaling, and the calyx splitting off, the lid, being now dry, blows off with the first blast of wind, and scatters the seeds, which by this time are hard and ripe.
When the seeds are ripe they are of a light colour, like white-brown paper, and incline to a triangular figure, whose angles are rounded off. They are depressed on both sides, so as to become pretty flat, and their whole surface is cellular; the cells have no particular form, but are somewhat irregular, and the ridges that form them are pretty eminent. As the drawing appears, the seeds may be said to have a basis and an apex; the former has no other particular mark than the cells, but the latter has a kind of notch indented downward from the top, which is the umbilicus of the seed. The parenchyma appears of a greyish colour. A middling grain is about a sixteenth of an inch long, and not quite so broad in the broadest part.
Cicer Rubrum.
Fig. 26 to 29. C. Arietinum. Linn. Chickpea. There is a good deal of reason for comparing the chiche grain to the head of a ram; for each of them, Fig. 26, consists of a round or back part, and an apex or snout. There are, besides this shape, which indeed favours the simile, several depressions upon the grain which add still to the likeness of that head; and these we shall consider in particular. On the upper or convex side there is, in most of them, a longitudinal little ridge, and a depression on each side, which resembles the rising in the frontal bone of a sheep; and, a little further forward, two risings, one on each side, which look like the superciliary eminences of the eyes. Each side of the round or occipital part has a depression that also adds to the same image; but what is yet a greater argument for it, is, that the under part, Fig. 27, is flattish, having an edge on each side, which may be compared to the edges of the under jaw. In the center of this flat part there is a little mamillary rising very remarkable, and just under the apex or snout an oval hole, whitish at the bottom, which is the umbilicus of the seed; besides which, there is an apparent sulcus on each side the apex, running a little way back, and is a close resemblance to the rictus oris. The husk is thin and fragile, and when taken off, looks like thin tortoise-shell; and the nucleus or parenchyma is of a yellowish white, exactly like the substance of a split-pea, without the covering. The entire nucleus has the same depressions which appear on its husk or cortex; and a fore view of it, Fig. 28, shews the naked apex, with the hole underneath, which is but superficial; and the seam which distinguishes the tip of the apex, I take to be the rudiment of the plant, for it is easily separated in that seam. The natural size of this seed appears, Fig. 29, being almost three-eighths of an inch from the apex to the outer edge of the basis, and something narrower.
Laurus.
Fig. 30, 31, 32. L. nobilis. Linn. Bay-berries. The bay-berries, Fig. 30, are a fruit of an oval shape, sticking to a short stem not above a quarter of an inch long; the surface is generally black, but some of them, whether through age I cannot say, are crusted over with a dull ash-coloured scurfy matter, and sometimes with fine ragged membranes. When the husk is opened, it appears of a fine dark-brown colour on the inner surface, being a smooth thin membrane that lines the husk, and at the smaller end it suddenly grows yellowish, and looks like a brown cup with a yellow bottom.
The nucleus easily comes out when the husk is opened, and as easily separates into two parts or lobes longitudinally; each of which is represented, Fig. 31. They lie in the husk with the flat surfaces together, each of which has a sinus at the smaller end shaped like the sole of one’s shoe; one of these contains the little piece which has the rudiments of the tree, adhering closely to its sinus; the other is empty, and serves only to give room to these rudiments when the flat surfaces of both lobes are together: Fig. 32 represents that little piece taken out and viewed by a larger magnifier, and appears to be convex on the visible side; having in its outline much the same form with the cell or sinus which contained it. It has a ridge in a longitudinal direction, is smaller at one end than the other, has risings on the sides, and is a most entertaining object.
Ficoides Afra.
Fig. 33, 34. Mesembryanthemum Crystallinum. Linn. Diamond Fig-marygold, or Ice-plant.[156] The whole stalks, leaves, and calix are covered with little glassy globules, which are called diamond or silver drops; and which are rather like ice than either. They are transparent, in as much as opposite windows of houses appear through them, and the green stalk makes those between it and the microscope look green. Those upon the stalks are spheroids, but those on the leaves and calix are globular. They seem like so many transparent stones set into a case, like those of a ring; others are more prominent. Upon breaking them, they appear to be little membranous bladders, very clear, and filled with an aqueous liquor. When they begin to wither and the juice to exhale, these membranes appear flaccid and collapsed.
[156] Dr. Parsons having given the microscopical description of the flower as well as the seed of this plant, and each of them forming a very agreeable object, the figure and description of the flower is here introduced.
Fig. 33 shews a flower of its natural size, with a bit of its stalk and a leaf; the leaf has its apex bent towards one side, is fat or thick, and has in its sinus the bud of another. The seed-vessel is also fleshy, and the calix has but three leaves, which is an exception to the general rule mentioned above, each of which has its apex in the center, or nearly so, differing from those of the stalk. The flower is indeed polypetalous, having an infinite number of narrow little leaves crowded together, of a whitish faint purple, in some parts nearly white, but very inconsiderable.
Fig. 34 is the seed, which is enlarged microscopically, having a streaky surface, and being of a triangular form. At one angle there is a dent or rictus, the end of which is the umbilicus of the seed. It is of a yellowish brown colour, and is very minute in its natural size, which is seen in those little specks near it.
Palma Arecifera.
Fig. 35, 36, 37. Areca Catechu. Linn. Syst. Vegetab. Areca Nut. The areca nut grows in a husk like the walnut or nutmeg. Fig. 35 is that hard nut which we are now to describe. Its surface is a dark brown, striated promiscuously with a yellowish brown colour; its figure a cone, and is capable of standing firmly upon its basis. In the center of the basis there is the hole or vestige of its pedicle, or whatever other thing stuck to it whilst inveloped in its husk, round which the bottom is whitish. Fig. 36 is another species of the areca nut, at least in shape, being somewhat less, more squat, and having no cone. I cannot say, whether these different shaped cones might not be a variation of the fruit of the same tree, as apples or any other fruits often are; but the surfaces are not precisely alike in one respect only, their colour being the same, that is, the yellowish brown lines upon the surface of the latter are thicker together, and sink deeper into the cortex between the dark brown parts, which are consequently made more imminent thereby than those of the conical one.
Upon cutting one of these into two parts, the surface appears at Fig. 37. On the outer part all round the internal substance appears radiated outward, being of a dark red and brown colour, and in its center inclosing a white substance, which in many places shoots itself out into the brown substance in little radii towards the cortex.
Juniperus.
Fig. 38, 39. J. Communis. Linn. Juniper Berry. Fig. 38, a, is a juniper berry magnified to shew its marks the more plainly. This fruit is quite round, of a black colour, which, although it appears smooth, yet the covering appears porous, and resembles the surface of shagreen in some measure. At the top it has a triangular sulcus, which is not very deep, and in some it is superficial. At the other extremity the stem appears, which is rough near the place of its insertion, with a scaly covering for a little space. b, is a transverse section of a juniper berry, which shews the thickness of the pulpy substance of the fruit, which appears every where interspersed and mixed with a great quantity of fine yellow gum, that in many places is in lumps, especially about the ossicula or stones of the fruit. This parenchyma incloses three of these ossicula, lying in close contact together by their flatter sides, and with their apices meeting at the top. c, is the fruit of its natural size, some grains may be a little bigger, some a little less.
Fig. 39 is the convex side of one of the stones, having from the apex three or four ridges, which render it triangular at the top, and are lost towards the basis, of an irregular form, long, narrow, and shining, after being cleansed of the pulp that covers them with the gummy matter just mentioned; but when dry, has an appearance like that of the stones of other fruit. Fig. 40 shews a longitudinal section of one of them, which brings to view a nucleus in all respects like that of a plumb-stone, being cloathed with a membrane, and having a succulent parenchyma. a, is the stone in its natural size.
Santonicum.
Fig. 41, 42. Artemisia S. Linn. Worm-seed. Fig. 41 shews the form of a middling seed enlarged by the microscope, for they are of different sizes among one another. This is one of the most singular in its structure, having scarce any thing substantial in it. The four little figures near it are those of a natural size, which are very small, and therefore renders the examination of them the more difficult. The seed has a small end or handle, being the place to which the stem which supports it was fixed, and the other end is bulky and round, having from the hoary handles several bulges all round, which are soft, and so very tender, that the rubbing of the seeds together reduces the surfaces to powder, whereby a large seed may be reduced to a very small one. The seed seems to be entirely composed of thin brittle membranes of an extreme delicate contexture, as at Fig. 42, having a dark center, from which it is transparent outward to the edge all round, and radiated upwards by infinitely fine radii, which do not render it in the least opake. Thus from the very outer surface the seed is composed of these sort of membranes, one after another, till nothing remains behind. Their colour before the naked eye is of a yellowish cast, but before the microscope for opake objects shines in many places like gold.
Scabiosa Major Vulgaris.
Fig. 43 to 46. S. Arvensis. Linn. Scabious. There is no seed perhaps which has more beauties than this of the scabious. Fig. 43 is a view of what botanists call one of the florets, which is a calix to the seed, whose fibres appear to extend themselves over its edges. This cup is of an octagonal form, and makes an appearance like a fine vase, having scallopped edges, and towards the inner part of the edge a whitish ruffled membrane. The ribs run down from its mouth, which is bell-fashioned, and becoming narrower downward, form obtuse angles, by continuing from the bend to form the bottom of the vase. Between these ribs down the bend the vase is clear, though not quite transparent, and from thence to the bottom the ribs are hairy, and make an agreeable figure.
Fig. 44 is the seed taken out of the vase, and drawn in another proportion, wherein appears first its thick body, which is somewhat hoary by the microscope, and runs up with a narrow neck, till it divides into five spiculated fibres, called by Gerard purple thrumbs, whose spiculæ or spines are determined upwards, and are thereby ready to cause the seed to recede from any thing that might injure it upon being touched. The bodies of the vases when first ripe are of a fine lemon yellow, but grow by long keeping darker; and the bason formed by the roots of the fine fibres is of a fine green, but the fibres themselves of a shining brown, like brown sugar-candy, as their spines are also.
Fig. 45 represents the stalk to which the vases stick by their bottoms, all which, when together, form the head mentioned by botanists to be the characters of some species of the scabious. In this figure the body of the stalk appears all stuck full of narrow whitish leaves, and the round spots between their roots are the vestiges of the bottoms of the vases; so that the leaves and vases are mixed together all over the stalk.
Fig. 46 shews a vase with a piece of its side cut out from the edge to the bottom. The bulbous part of the seed is contained in a delicate white membranous case, arising from the inner membrane of the bottom of the vase, and running up about half way the neck of the seed, embracing it pretty close, with a mouth consisting of six or eight sides as beautifully formed as that of any fine cut-glass decanter. The seed is loose in this theca, so that it may be turned round within it, but cannot be pulled out without tearing this beautiful theca, upon account of its narrow neck.
CHAP. XII.
INSTRUCTIONS FOR COLLECTING AND PRESERVING INSECTS—A COPIOUS LIST OF MICROSCOPIC OBJECTS. BY THE EDITOR.
Those who have been long accustomed to microscopical investigations will readily admit, that the numerous class of insects, and their several parts, afford some of the most diversified, as well as the most admirable objects for the microscope. To readers of this description, who should be considered as adepts, the following instructions may possibly afford little that is novel, as by constant habit they must be thoroughly conversant in the best manner of procuring and preserving the various objects; it may be, however, reasonably presumed, that there are many persons who have not hitherto devoted their attention to this subject, as well as numbers who, deterred by the imaginary difficulties attending it, have either totally relinquished the pursuit, or made but small progress therein; to such, the directions here given it is hoped will prove an acquisition.
Confident as I am of the delights which this employment affords to the intelligent and industrious admirer of the works of nature, it is to be deplored that so many persons, who possess every requisite for these enjoyments, should remain totally insensible to their attractions; how much might be atchieved, could such be prevailed upon to devote their hours of leisure to so rational a purpose? especially if it be considered how easily these pleasures are to be attained, as well as the tranquillity with which they may be enjoyed.
Investigations of this kind particularly recommend themselves to the attention of the ladies, as being congenial with that refinement of taste and sentiment, and that pure and placid consistency of conduct which so eminently distinguish and adorn those of this happy isle. To the honour of several ladies of eminence be it recorded, that they are proficients in the study of the various branches of natural history, and many others are making considerable progress in this pleasing science; than which, none can possess a greater tendency to sweeten the hours of solitude and anxiety. How infinitely superior to a rational mind is the gratification arising from such pursuits, to those, to which numbers unhappily sacrifice their health and beauty, and frequently the peace of mind of themselves and relatives, by a baneful attachment to the gaming table; and that not owing to intellectual incapacity, but merely from not possessing fortitude sufficient to prefer the improvement of their minds to amusements, for which no better plea can possibly be urged, than that of their being sanctioned by the idol, Fashion.
Actuated by no other motives, than the sincerest respect I entertain for my fair countrywomen, and anxiety for their real welfare, I have presumed thus freely to deliver my sentiments; with greater confidence in the merits of the cause I plead, and reliance on their prudent discrimination, than on the persuasive eloquence of the advocate, I am willing to flatter myself that these remarks may not be entirely ineffectual; at least in warning those who have happily as yet escaped so dangerous a gulf.
Again, how many of my own sex, divested of a taste for rational enjoyments, groan under the oppressive load of listlessness and dissatisfaction; for, independent of the more serious and requisite duties of our respective callings, we require amusements to refresh us in our vacant moments, which if not devoted to some laudable pursuit, will necessarily, like those of too many of our young men of fortune, be sauntered away, or consumed in senseless and illicit delights, eventually productive of infallible ruin to both body and mind; viewed in this light, it may indeed be said, that the situation of men of opulence is of all stations the least to be envied. I cannot, therefore, but earnestly recommend to those entrusted with that important charge, the education of youth, to enforce both by precept and example, their employment of that time which is not engaged in necessary avocations, to some purpose, that, whilst it amuses, may likewise instruct and improve their understandings. These measures are more peculiarly important in times like the present, when idleness, dissipation, and infidelity are with gigantic strides endeavouring to encompass mankind with chains of slavery of all others the most dreadful and pernicious.
I shall close these observations in the elegant language of an admired writer.
“A man that has formed a habit of turning every new object to his entertainment, finds in the productions of nature an inexhaustible stock of materials upon which he can employ himself, without any temptations to envy or malevolence; faults, perhaps, seldom totally avoided by those whose judgment is much exercised upon the works of art. He has always a certain prospect of discovering new reasons for adoring the sovereign Author of the universe, and probable hopes of making some discovery of benefit to others, or profit to himself. There is no doubt but many vegetables and animals have qualities that might be of great use, to the knowledge of which there is not required much force of penetration or fatigue of study, but only frequent experiments and close attention. What is said by the chemists of their darling mercury, is, perhaps, true of every body through the whole creation, that, if a thousand lives should be spent upon it, all its properties would not be found out.
“Mankind must necessarily be diversified by various tastes, since life affords and requires such multitudes of employments, and a nation of naturalists is neither to be hoped or desired; but it is surely not improper to point out a fresh amusement to those who languish in health, and repine in plenty, for want of some source of diversion that may be less easily exhausted, and to inform the multitudes of both sexes, who are burthened with every new day, that there are many shews which they have not seen. He that enlarges his curiosity after the works of nature, demonstrably multiplies the inlets to happiness.”[157]
[157] Johnson.
The characters by which the several classes of insects are distinguished, have been already explained in [pages 218] and [219]; their transformations have likewise been fully described; I shall now proceed to enumerate the best methods of obtaining them in their different states. Justice to the merits of two eminent naturalists[158] obliges me to mention, that to them I am indebted for a considerable part of these instructions.
[158] Lettsom’s Naturalist’s Companion; Curtis’s Instructions for Collecting and Preserving Insects. Both these tracts are now become very scarce.
Of all the different classes or orders of insects, that called LEPIDOPTERA is not only one of the most numerous, but the most beautiful, with respect to the variety as well as richness of their colours; and, as from the peculiar delicacy of their structure, they require greater care to be used in catching, as well as in preserving them, it will be proper first to speak of, and be more particular in the directions concerning them.