« ÎnapoiContinuați »
uniform in the same species, or even genus. They enfold the embryo plant.
III. TRUNK. The trunk of trees includes the stems or stalks, which are of seven kinds. The stem as it advances in growth, is either able to support itself, or twines round other bodies. It is either simple as in the lily; or branched as in other plants. The parts are: 1. Cuulis, the stem which bears both leaves and flowers, as the trunks and branches of all trees and shrubs, as well as of many herbaceous plants. 2. Culmus, a straw or culm, the peculiar stem of grasses, rushes, and similar plants. 3. Scapus or': stalk, springs immediately from the root, bearing flowers and fruit but not leaves, as in the primrose or cowslip. 4. Pedunculus, the flower-stalk, springs from the stem or branches, bearing flowers and fruit, but not leaves. 5. Petiolus, the foot-stalk, is applied exclusively to the stalk of a leaf.
IV. LEAVES. These are generally so formed as to present a large surface to the atmosphere. When they are of any other hue than green, they are said, in botanical language, to be coloured. The internal surface of a leaf is highly vascular and pulpy, and is clothed with a cuticle very various in different plants; but its pores are always so constructed as to admit of the requisite evaporation or absorption of moisture, as well as to admit and give out air. Light also acts through this cuticle, in a different manner. The effect of moisture must have been observed by every one. By absorption from the atmosphere, the leaves are refreshed; but by evaporation, especially when separated from their stalks, they soon fade and wither. The nutritious juices, imbibed from the earth and become sap, are carried by appropriate vessels into the substance of the leaves, and these juices are returned from each leaf, not into the wood again, but into the bark.* The sap is carried into the leaves for the purpose of being acted upon by air and light, with the assistance of heat and moisture. By all these agents, a most material change is wrought in the component parts of the sap, according to the nature
*This is effected by a double set of vessels, analogous to the arteries and veins in animals, and is the circulation of the vegetable blood or sap.
of the secretions which are elaborated, whether resinous, oily, mucilaginous, saccharine, bitter, acrid, or alkaline. The green colour of the leaves is almost entirely owing to the action of light, as was before observed. Leaves are subject to a sort of disease by which they become partially spotted or streaked, as with white or yellow, and in this state are termed variegated. The irritable nature of leaves is very extraordinary. The mimosa pudica or sensitive plant, common in hot-houses, when touched by any extraneous body, folds up its leaves one after another, while the foot-stalks droop, as if dying.
V. PROPS or fulcra. These are: 1. Stipula, a leafyappendage to the true leaves or to their stalks, for the most part in pairs. 2. Bractea, a leafy appendage to the flower or its stalk, very conspicuous in the lime-tree, 3. Spina, a thorn proceeding from the wood itself as in the wild pear-tree, which loses its thorns by cultivation. 4. Aculeus, a prickle, proceeding from the bark only as in the rose and bramble. 5. Cirrus, a tendril or clasper, is a support for weak stems, and enables them to climb rocks, or the trunks of lofty trees. 6. Glandula, a gland is a small tumour secreting a sweet, resinous, or fragrant liquor, as on the calyx or cup of the moss-rose, and the foot-stalks of passion-flowers. 7. Pilus, a hair, which includes all the various kinds of pubescence; bristles, wool, &c. some of which discharge a poison, as in the nettle; causing great irritation whenever they are so touched, that their points may wound the skin.
VI. INFLORESCENCE, or the different kinds or modes of flowering are, I. Verticillus, a whorl, in which the flowers surround the stem in a garland or ring, as in the mints, dead-nettle, &c. 2. Racemus, a cluster, bears several flowers each on its own stalk, like a bunch of currants. 3. Spica, a spike is composed of numerous crowded flowers, ranged along an upright, common stalk, expanding progressively, as in wheat and barley. 4. Corymbus, a corymb, is a flat-topped spike as in the cabbage and wall-flower. 5. Fasciculus, a close bundle of flowers, as in the sweet-william. 6. Capitulum, a head or tuft, as in the globe-amaranthus and thrift. 7. Umbella, an umbel, consists of several stalks, called rays, spreading like an umbrella, as in parsley, carrot, and hemlock. 8.
Cyma, a cyme, or stalks springing from a common centr and afterwards irregularly subdivided, as in the laurustinus and elder. 9. Paniculus, panicle, a loose subdivided bunch of flowers, as in the oat. 10. Thyrsus, a bunch, is a very dense panicle inclining to an oval figure, as in the lilac.
VII. FRUCTIFICATION. Under this term are comprehended not only the parts of the fruit, but also those of the flower, which last are indispensable for bringing the former to perfection. The parts of fructification are, 1. Calyx, a flower-cup, or external covering of the flower: to which belong the perianthium: involucrum; amentum or cat-kin; spatha, or sheath; gluma, or husk; perichoe tium or scaly sheath; and volva, the wrapper. 2. Corolla,, is situated within the calyx, and consists in general of the coloured leaves of a flower;-the petalum, or petal, and the nectarium, or nectary, belong to the corolla. 3. Stumina, the stamens, are various in number, in different flowers, and are situated withinside of the corolla. The stamen consists of a filamentum or filament, and the anthera or anther. The cells of the latter contain the pollen or fecundating dust. 4. Pistilla, the pistils stand in the centre of the circle formed by the stamens, and consist of the germen or rudiments of the future fruit or seed; the style, which elevates the stigma; and the stigma which is destined to receive the pollen. 5. Pericarpium, the seedvessel is formed from the germen eularged, and is of the following kinds: a capsular or capsule; siliqua, or pod; legumen or legume, the fruit of the pea-kind; drupa, stone-fruit; ponium, an apple; bacca, a berry; and strobilus, a cone. 6. Semina, the seeds are composed of the embryo or germ, called by Linnæus, corculum, or little heart; the cotyledones, or seed-lobes almost universally, two in number; * albumen, the white; vitellus, the yolk; testa, the skin; and hilum, the scar. Seeds are often accompanied by appendages or accessory parts; as, pelli
* M. Jussieu, a French botanist of the first eminence, has divided all plants into acotyledones, or such as are destitute of a cotyledon; monocotyledones, such as have one cotyledon; and dicotyledones, such as have two.
cula, the pellicle; aillus, the tunic; pappus, the seeddown; cauda, a tail; rostrum, a beak. To which may be added various spines, hooks, scales, and crests, generally serving to attach such seeds as are furnished with then, to the rough coats of animals, and thus promote their dispersion. 7. Receptaculum, the receptacle, is the base which receives the other parts of the fructification. It is proper when it supports the parts of a single fructification only; when it is a base to which only the parts of the flower are joined, and not the germen, it is called a receptacle of the flower; in this case the germen being placed below the receptacle of the flower, has a base of its own, which is called the receptacle of the fruit, and it is termed a receptacle of the seeds, when it is a base to which the seeds are fastened within the pericarpium. It is called common when it supports a head of flowers.
VIII. CLASSIFICATION. The system of Linnæus, now generally acknowledged and adopted, is founded on the number, situation, and proportion of the stamens and pistils, whose uses and structure have been just explained. The following twenty-four classes owe their distinctions principally to the stamens. 1. Monandria, one stamen. 2. Diandria, two stamina. 3. Triandria, three. 4. Tetrandria, four. 5. Pentandria, five. 6. Hexandria, six. 7. Heptandria, seven. 8. Octandria, eight. 9. Enneandria, nine. 10. Decandria, ten. 11. Dodecandria, twelve. 12. Icosandria, twenty or more stamina, inserted into the calyx. 13. Polyanrida, all above twenty inserted into the receptacle. 14. Didynamia, four stamina, two long and two short. 15. Tetradynamia, six stamina, four long and two short. 16. Monadelphia, the stamina united into one body by the filaments. 17. Diadelphia, the stamina united into the bodies by the filaments. 18. Polyadelphia, the stamina united into three or more bodies by the filaments. 19. Syngenesia, anthers united into a tube. 20. Gynandria, stamens inserted either upon the style or germen. 21. Monoecia, stamens and pistils in separate flowers, but on the same plant. 22. Dioecia, stamens and pistils, like the former in separate flowers, but on two separate plants. 23. Polygamia, stamens and pistils
separate in some flowers, united in others, either on one, two, or three distinct plants. 24. Cryptogamia, stamens and pistils, either not well ascertained, or not to be numbered with certainty.
The orders, or subdivisions of the classes are generally marked by the number of the pistils, or by some other circumstances equally intelligible. The names of these as well of the classes, are both of Greek derivation, and designate the functions of the respective organs.
The student in botany has a rich source of innocent pleasure. He would find himself, says Dr. Smith, neither solitary nor desolate, had he no other companion than a
mountain daisy,' that modest crimson-tipped flower,' so sweetly sung by one of nature's own poets. The hum blest weed or moss will ever afford him something to examine or illustrate, and a great deal to admire. Introduce him to the magnificence of a tropical forest, the enamelled meadows of the Alps, or the wonders of New Holland, and his thoughts will not dwell much upon riches or literary honours. Whether (adds the same author) we scrutinize the damp recesses of woods in the wintry months, when the numerous tribe of mosses are displaying their minute, but highly interesting structure ;-whether we walk forth in the early spring, when the ruby tips of the hawthorn bush, give the first sign of its approaching vegetation, or a little after, when the violet, welcomes us with its scent, and the primrose with its beauty;--we shall always find something to study and admire in their cha racters. The yellow blossoms of the morning that fold up their delicate leaves as the day advances, others that court and sustain the full blaze of noon-and the pale night-scented tribe which expand and diffuse their sweet fragrance towards evening,--all have peculiar charins. The more we study the works of the Creator, the more wisdom, beauty, and harmony, become manifest, even to our limited apprehensions-and while we admire, it is impossible not to adore.
Soft roll your incense, herbs, and fruits and flowers,