Vegetable Anatomy, or the Structure and Organization of Plants.

1278. Vegetables may be classed for the study of their anatomy and physiology, according as they are distinguished by a structure or organization more complicated or more simple. The former will constitute what may be denominated perfect plants, and will form a class comprehending the principal mass of the vegetable kingdom. The latter will constitute what may be denominated imperfect plants, and will form a class comprehending all such vegetables as are not included in the foregoing class. We shall first consider their external, and next their internal organization.

SECT. I. Of the External Structure of Perfect Plants.

1279. The parts of perfect plants may be distributed into conservative and reproductive, as corresponding to their respective functions in the economy of vegetation.

1280. The conservative organs are such as are absolutely necessary to the growth and preservation of the plant, and include the root, trunk, branch, leaf, and frond.

1281. The root is that part of the plant by which it attaches itself to the soil in which it grows, or to the substance on which it feeds, and is the principal organ of nutrition.

1282. The trunk is that part of the plant which, springing immediately from the root, ascends in a vertical position above the surface of the soil, and constitutes the principal bulk of the individual.

1283. The branches are the divisions of the trunk, originating generally in the upper extremity, but often also along the sides.

1284. The leaf, which is a temporary part of the plant, is a thin and flat substance of a green color, issuing generally from numerous points towards the extremities of the branches, but sometimes also immediately from the stem or root, and distinguishable by the sight or touch into an upper and under surface, a base and apex, with a midrib and lateral nerves.

1285. The frond, which is to be regarded as a compound of several of the parts already described, consists of an union or incorporation of the leaf, leaf-stalk, and branch or stem, forming as it were but one organ, of which the constituent parts do not separate spontaneously from one another by means of the fracture of any natural joint, as in the case of plants in general, but adhere together even in their decay. It is found in palms and ferns.

1286. The conservative appendages are such accessory or supernumerary parts as are found to accompany the conservative organs occasionally, but not invariably. They are permanent in whatever species they are found to exist; some being peculiar to one species, and some to another. But they are never found to be all united in the same species, and are not necessarily included in the general idea of the plant. They are denominated gems, glands, tendrils, stipulæ, armature, pubescence, and anomalies.

1287. Gems or bulbs are organized substances issuing from the surface of the plant, and containing the rudiments of new and additional parts which they protrude; or the rudiments of new individuals which they constitute by detaching themselves ultimately from the parent plant, and fixing themselves in the soil.

1288. Glands are small and minute substances of various different forms, found chiefly on the surface of the leaf and petiole, but often also on the other parts of the plant, and supposed to be organs of secretion. 1289. The tendril is a thread-shaped and generally spiral process issuing from the stem, branch, or petiole, and sometimes even from the expansion of the leaf itself, being an organ by which plants of weak and climbing stems attach themselves to other plants, or other substances for support; for which purpose it seems to be well fitted by nature, the tendril being much stronger than a branch of the same size.

1290. The stipule are small and foliaceous appendages accompanying the real leaves, and assuming the appearance of leaves in miniature.

1291. Ramenta are thin, oblong, and strap-shaped appendages of a brownish color, issuing from the surface of the plant, and somewhat resembling the stipule, but not necessarily accompanying the leaves. 1992. The armature consists of such accessory and auxiliary parts as seem to have been intended by nature to defend the plant against the attacks of animals.

1293. The pubescence is a general term, including under it all sorts of vegetable down or hairiness, with which the surface of the plant may be covered, finer or less formidable than the armature. 1294. Anomalies. There

are several other appen. dages proper to conservative organs, which are so totally different from all the foregoing, that they cannot be classed with any of them; and so very circumscribed in their occurrence, that they do not yet seem to have been designated by any peculiar appellation. The first anomaly, as affects the conservative appendages, occurs in dionoea muscipula or Venus's fly-trap (fig. 217 a). A second is that which oc curs in sarracenia pur

purea or purple side-sad

dle-flower (b). A third, which is still more singular, occurs in nepenthes distillatoria (c). The last anomaly

is that of a small globular and membranaceous bag, attached as an appendage to the roots and leaves of some of the aquatics. It is contined only to a few genera, but is to be seen in great abundance on the roots or leaves of the several species of utricularia inhabiting the ponds and ditches of this country; and on the leaves of aldrovanda vesiculosa, an inhabitant of the marshes of Italy. In utricularia vulgaris this appendage is pear-shaped, compressed with an open border at the small end, furnished with several alender fibres originating in the margin, and containing a transparent and watery fluid, and a small bubble of air, by means of which it seems to acquire a buoyancy that suspends it in the water.

1295. The reproductive organs are such parts of the plant as are essential to its propagation, whose object is the reproduction of the species, terminating the old individual, and beginning the new. It includes the flower, with its immediate accompaniments or peculiarities, the flower-stalk, receptacle, and inflorescepce, together with the ovary or fruit.

1996. The flower, like the leaf, is a temporary part of the plant, issuing generally from the extremity of the branches, but sometimes also from the root, stem, and even leaf, being the apparatus destined by nature for the production of the fruit, and being also distinguishable, for the most part, by the brilliancy of its coloring or the sweetness of its smell.

1291. The flower-stalk is a partial trunk or stem, supporting one or more flowers, if the flowers are not sessile, and issuing from the root, stem, branch, or petiole, and sometimes even from the leaf.

1998. The receptacle is the seat of the flower, and point of union between the different parts of the flower, or between the flower and the plant, whether immediate and sessile, or mediate and supported upon a cwer-stalk.

1999. The inflorescence, mode of flowering, is the peculiar mode of aggregation in which flowers are arranged or distributed upon the plant.

15. The fruit is the ripened ovary, or seed-vessel which succeeds the flower. In popular language the term is confined chiefly to such fruits as are esculent, as the apple, the peach, and the cherry; but with the botanist the matured ovary of every flower, with the parts contained, constitutes the fruit.

1301. Appendages. The reproductive organs, like the conservative organs, are often found to be furnished with various additional and supernumerary parts, not at all essential to their constitution, because not always present, and hence denominated appendages. Many of them are precisely of the same character with that of the conservative appendages, except that they are of a finer and more delicate texture. Such are the glands, down, pubescence, hairs, thorns or prickles, with one or other of which the parts of the fructification are occasionally furnished. But others are altogether peculiar to the reproductive organs, and are to be regarded as constituting, in the strict acceptation of the term, true reproductive appendages. Some of them are found to be proper to the flower, as the involucre, spathe, bracte, &c., and others to the fruit as the persisting calyx, exemplified in the pomegranate.

SECT. II. Of the External Structure of Imperfect Plants.

1302. Plants apparently defective in one or other of the more conspicuous parts or organs, whether conservative or reproductive, are denominated imperfect. The most generally adopted division of imperfect plants is that by which they are distributed into filices, equisitaceæ, lycopodinæ, musci, hepaticæ, algæ, lichenæ, and fungi.

1505. The filices, cquisitace, and lycopodina, are for the most part herbaceous, and die down to the ground in the winter, but they are furnished with a perennial root, from which there annually issues a frond bearing the fructification. The favorite habitations of many of them are heaths and uncultivated grounds, where they are found intermixed with furze and brambles; but the habitations of such as are the most luxuriant in their growth are moist and fertile spots, in shady and retired situations, as on mossy dripping rocks, or by fountains and rills of water. Some of them will thrive even on the dry and barren rock, or in the chinks and fissures of walls; and others only in wet and marshy situations where they are half immersed in water.

1304. The mosses (fig. 218.) are a tribe of imperfect plants of a small and diminutive size, consisting often

merely of a root, surmounted with a tuft of minute leaves, from the centre of which the fructification springs, but furnished for the most part with a stem and branches, on which the leaves are closely imbricated, and the fructification terminal or lateral. They are perennials and herbaceous, approaching to hrubby; or annuals, though rarely so, and wholly herbaceous, the perennials being also evergreens. 1306. The hepatica are a tribe of small and herbaceous plants resembling the mosses, but chiefly constituting fronds, and producing their fruit in a capsule that splits into longitudinal valves. In their habita

tions, they affect for the most part the same sort of situations as the mosses, being found chiefly in wet and shady spots, by the sides of springs and ditches, or on the shelving brinks of rivulets, or on the trunks of trees. Like the mosses, they thrive best also in cold and damp weather, and recover their verdure though dried, if moistened again with water.

1306. The algae, or sea-weeds, include not merely marine and many other immersed plants, but also a great variety of plants that are not even aquatics. All the alga, agree in the common character of having their herbage frondose, or but rarely admitting of the distinction of root, stem, and leaf.

1307. The utility of the algae is obviously very considerable, whether we regard them as furnishing an article of animal food, or as applicable to medicine and the arts. The fucus sac

charinus (fig. 219 a.), palmatus (b), and edulis (c), and several other fuci, are eaten and much relished by many people, whether raw or dressed, and it is likely that some of them are fed upon by various species of fish. The fucus lichenoides (Turner, c. 118.) is now believed to be the chief material of the edible nests of the East India swallows, which are so much esteemed for soups, that they sell in China for their weight in gold. When disengaged from their place of growth and thrown upon the sea-shore, the European algæ are often collected by the farmer and used as manure. They are often also employed in the preparation of dyes, as well as in the lucrative manufacture of kelp, a commodity of the most indispensable utility in the important arts of making soap and glass.

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1308. The utility of the lichene is also worthy of notice. The lichen rangiferinus forms the principal nourishment of the reindeer during the cold months of winter, when all other herbage fails. The lichen islandicus is eaten by the Icelanders instead of bread, or used in the preparation of broths, and, like the lichen pulmonarius, has been lately found to be beneficial in consumptive affections. Many of them are also employed in the preparation of some of our finest dyes, or pigments; and it is from the lichen parellus that the chemical analysist obtains his litmus. The lichens and the mosses seem instituted by nature to provide for the universal diffusion of vegetable life over the whole surface of the terrestrial globe. The powdery and tuberculous lichens attach themselves even to the bare and solid rock. Having reached the maturity of their species, they die and are converted into a fine earth, which forms a soil for the leathery lichens. These again decay and moulder into dust in their turn; and the depth of soil, which is thus augmented, is now capable of nourishing and supporting other tribes of vegetables. The seeds of the mosses lodge in it, and spring up into plants, augmenting also by their decay the quantity of soil, and preparing it for the support of plants of a more luxuriant growth, so that in the revolution of ages even the surface of the barren rock is covered with a soil capable of supporting the loftiest trees.

1309. The fungi are a tribe of plants whose herbage is a frond of a fleshy or pulpy texture, quick in its growth, and fugacious in its duration, and bearing seeds or gems in an appropriate and exposed membrane, or containing them interspersed throughout its mass. They are also a tribe of plants that may be regarded as the lowest in the vegetable scale, exhibiting a considerable resemblance to the tribe of zoophites, and thus forming the connecting link between the vegetable and animal kingdoms. The habitations they affect are very various, many of them vegetating on the surface of the earth (fig. 220 a), and some of them even buried under it; others on stumps and trunks of rotten trees (b); others on decayed fruit; others on damp and wet walls; and others on animal ordure.

1310. Uses of the fungi. The powder of the lycoperdons is said to be

an excellent optic; and is remarkable also for its property of strongly repelling moisture. If a basin filled with water, and a little of the powder strewed upon the surface so as to cover it only, the hand may be plunged into it and thrust down to the bottom without being wetted with a single drop of water. Several of the boleti, when dried, afford a very useful tinder; and several of the agarics and tubers are used as articles of food, or as ingredients in the preparation of seasoning. The truffle (fig. 221.) is much

esteemed for the rich and delicate flavor which it imparts to soups and sauces; and the mushroom (fig. 222.) and morel (fig. 223.) for their esculent property, and utility in the preparation of ketchup.

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221

222

SECT. III. Of the Internal Structure of Plants.

1311. The organs of plants discoverable by external examination, are themselves reducible in component organs, which are again resolvable into constituent and primary organs. These are called the decomposite, the composite, and the elementary.

SUBSECT. 1. Decomposite Organs.

1312. The decomposite organs constitute the vegetable individual, and are distinguishable on external examination; to the dissection of which we will now proceed, in the order of the seed, pericarp, flower, leaf, gem, and caudex, or branch, stem, and root, with their decomposite appendages.

1313. The secd. The mass of the seed consists of two principal parts, distinguishable without much dif. ficulty; namely, the integuments and nucleus, or embryo and its envelopes.

1514. The integuments proper to the seed are two in number, an exterior integument and an interior in

tegument.

1315, The exterior integument, or testa, is the original cuticle of the nucleus, not detachable in the early stages of its growth, but detachable at the period of the maturity of the fruit, when it is generally of a membranaceous or leathery texture; though sometimes soft and fleshy, and sometimes crustaceous and bony. It may be very easily distinguished in the transverse or longitudinal section of the garden-bean or any other large seed.

1316. The interior integument, or sub-testa, lines the exterior integument, or testa, and immediately envelopes the nucleus. Like the testa, to which indeed it adheres, it may be easily distinguished in the garden-bean (fig. 224), or in a ripe walnut; in which last it is a fine transparent and net-like membrane. 1517. The nucleus is that part of the seed which is 224 contamed within the proper integuments, consisting of the albumen with the vitellus, when present, and embryo.

1318 The albumen is an organ resembling in its consistence the white of an egg, and forming, in most cases, the exterior portion of the nucleus, but always separable from the interior or remaining portion.

1519. The vitellus is an organ of a fleshy but firm contexture, situated, when present, between the albumen and embryo; to the former of which it is attached only by adhesion, but to the latter by incorporation of substance, so as to be inseparable from it, except by force.

150. The embryo (a), which is the last and most essential part of the seed and final object of the

fructification, as being the germ of the future plant, is a small and often very minute organ, enclosed within the albumen and occupying the centre of the seed.

121. The cotyledon or seed-lobe (b), is that portion of the embryo that encloses and protects the plantlet, and springs up during the process of germination into what is usually denominated the seminal leaf, if the lobe is solitary; or seminal leaves, if there are more lobes than one. In the former case the seed is said to be monocotyledonous; in the latter case, it is said to be dicotyledonous. Dicotyledonous seeds, which constitute by far the majority of seeds, are well exemplified in the garden-bean. As there are some seeds whose cotyledon consists of one lobe only, falling short of the general number, so there are also a few whose cotyledon is divisible into several lobes, exceeding the general number. They have been denominated polycotyledonous seeds, and are exemplified in the case of lepidium sativum or common garden-cress, in which the lobes are six in number; as in that also of the different species of the genus pous, in which they vary from three to twelve.

1922 The plantlet, or future plant in miniature, is the interior and essential portion of the embryo, and seat of vegetable life. In some seeds it is so minute as to be scarcely perceptible; while in others it is so large as to be divisible into distinct parts, as in the garden-bean.

23. The pericarp, which in different species of fruit assumes so many varieties of contexture, acquires its several aspects, not so much from a diversity of substance as of modification.

1324. The valves of the capsule, but particularly the partitions by which it is divided into cells, are composed of a thin and skinny membrane, or of an epidermis covering a pulp more or less indurated, and in

terspersed with longitudinal fibres. The capsule of the mosses is composed of a double and net-like mem. brane, enclosed within a fine epidermis.

1325. The pome is composed of a fine but double epidermis, or, according to Knight, of two skins, enclosing a soft and fleshy pulp, with bundles of longitudinal fibres passing through it, contiguous to, and in the direction of, its longitudinal axis.

1326. The valves of the legume are composed of an epidermis enclosing a firm but fleshy pulp, lined for the most part with a skinny membrane, and of bundles of longitudinal fibres, forming the seam.

1827. The nutshell, whether hard or bony, or flexible and leathery, is composed of a pulp more or less highly indurated, interspersed with longitudinal fibres, and covered with an epidermis.

1328. The drupe is composed of an epidermis enclosing a fleshy pulp, which is sometimes so interwoven with a multiplicity of longitudinal fibres as to seem to consist wholly of threads, as in the cocoa-nut. 1329. The berry is composed of a very fine epidermis enclosing a soft and juicy pulp.

1330. The scales of the strobile are composed of a tough and leathery epidermis, enclosing a spongy but often highly indurated pulp interspersed with longitudinal fibres that pervade also the axis.

1331. The flower-stalk, or peduncle supporting the flower, which is a prolongation of the stem or branch, or rather a partial stem attached to it, if carefully dissected with the assistance of a good glass, will be found to consist of the following several parts:- 1st, An epidermis, or external envelope; 2dly, A parenchyma, or soft and pulpy mass; 3dly, Bundles of longitudinal threads or fibres, originating in the stem or branch, and passing throughout the whole extent of the parenchyma. The several organs of the flower are merely prolongations of the component parts of the flower-stalk, though each organ does not always contain the whole of such component parts, or at least not under the same modifications. The epidermis, however, and parenchyma are common to them all; but the longitudinal threads or fibres are seldom, if ever, to be found, except in the calyx or corolla.

1332. The leaf-stalk, or petiole supporting the leaf, which is a prolongation of the branch or stem, or rather a partial stem attached to it, exhibits upon dissection the same sort of structure as the peduncle, namely, an epidermis, a pulp or parenchyma, and bundles of longitudinal threads or fibres.

1333. Gems. There exists among the different tribes of vegetables four distinct species of gems, two peculiar to perfect plants, the bud and bulb, and two peculiar to imperfect plants, the propago and gongylus; the latter being denominated simple gems, because furnished with a single envelope only; and the former being denominated compound gems, because furnished with more than a single envelope.

1334. Buds are composed externally of a number of spoonshaped scales overlapping one another, and converging towards a point in the apex, and often cemented together by means of a glutinous or mucilaginous substance exuding from their surface. If these scales are stripped off and dissected under the microscope, they will be found to consist, like the leaves or divisions of the calyx, of an epidermis enclosing a pulp interspersed with a net-work of fibres, but unaccompanied with longitudinal threads. If the scales of a leaf-bud are taken and stripped off, and the remaining part carefully opened up, it will be found to consist of the rudiments of a young branch terminated by a bunch of incipient leaves imbedded in a white and cottony down, being minute but complete in all their parts and proportions, and folded or rolled up in the bud in a peculiar and determinate manner.

1335. Bulbs, which are either radical or caulinary, exhibit in their external structure, or in a part of their internal structure that is easily detected, several distinct varieties, some being solid, some coated, and some scaly; but all protruding in the process of vegetation the stem, leaf, and flower, peculiar to their species.

1336. The propage, which is a simple gem, peculiar to some genera of imperfect plants, and exemplified by Gaertner in the lichens, consists of a small and pulpy mass forming a granule of no regular shape, sometimes naked, and sometimes covered with an envelope, which is a fine epidermis.

1337. The gongylus, which is also a simple gem peculiar to some genera of imperfect plants, and exemplified by Gartner in the fuci, consists of a slightly indurated pulp moulded into a small and globular granule of a firm and solid contexture, and invested with an epidermis.

1338. The cauder includes the whole mass or body both of the trunk and root; its internal structure, like its external aspect or habit, is materially dif ferent in different tribes of plants.

1339. The first general mode of the Internal structure of the caudex is that in which an epidermis encloses merely a homogeneous mass of pulp or slender fibre. This is the simplest mode of internal structure existing among vege tables; it is exemplified in the lower orders of imperfect plants, particularly the algae and fungi.

1340. The second general mode of internal structure of the cauder is that in which an epidermis encloses two or more substances, or assemblages of sub stances, totally heterogeneous in their character. A very common variety of this mode is that in which an epidermis or bark encloses a soft and pulpy mass, interspersed with a number of longitudinal nerves or fibres, or bundles of fibres, extending from the base to the apex, and disposed in a peculiarity of

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manner characteristic of a tribe or genus. This mode prevails chiefly in herbaceous and annual or biennial plants. (fig. 225.) A second variety of this mode is that in which a strong and often thick bark encloses a circular layer of longitudinal fibres, or several such circular and concentric layers, interwoven with thin transverse and divergent layers of pulp, so as to form a firm and compact cylinder, in the centre of which is lodged a pulp or pith. This mode is best exemplified in trees and shrubs (fig. 26.), though it is also applicable to many plants whose texture is chiefly or almost wholly herbaceous, forming as it were the connecting link between such plants as are purely herbaceous on the one hand, and such as are purely woody on the other. In the latter case the wood is perfect; in the former case it is imperfect. The wood being imperfect in the root of the beet, the common bramble, and burdock; and perfect in the oak or alder.

1541. The appendages of the plant, whether conservative or reproductive, exhibit nothing in their internal structure that is at all essentially different from that of the organs that have been already described.

SUBSECT. 2. Composite Organs.

1342. The composite organs are the epidermis, pulp, pith, cortical layers, ligneous layers, and vegetable fibre, which may be further analysed, as being still compound, with a view to reach the ultimate and elementary organs of the vegetable subject.

1343. Structure of the vegetable epidermis. The epidermis of the vegetable, which, from its resemblance to that of the animal, has been designated by the same name, is the external envelope or integument of the plant, extending over the whole surface, and covering the root, stem, branches, leaves, flower, and fruit, with their appendages; the summit of the pistil only excepted. But although it is extended over the whole surface of the plant, it is not of equal consistence throughout. In the root and trunk it is a tough and leathery membrane, or it is a crust of considerable thickness, forming a notable portion of the bark, and assuming some peculiar shade of color; while in the leaves, flowers, and tender shoots, it is a fine, colorless, and transparent film, when detached; and when adherent, it is always tinged with some peculiar shade, which it borrows from the parts immediately beneath it.

1344. The pulp is a soft and juicy substance, constituting the principal mass of succulent plants, and a notable proportion of many parts even of woody plants. It constitutes the principal mass of many of the fungi and fuci, and of herbaceous plants in general. Mirbel compares it to clusters of small and