446 A perfed hen's egg is an organized body, pervaded by veffels, endowed with excitability, and replete with a moveable fluid, inclofing under divers membranes the animal in miniature. The egg-thell is almost entirely filled with a glutinous fubftance, laid up for the nourishment of the fatal animal.t If the egg be kept in a certain degree of warmth, whether by the natural heat of the parent animal, or by art, it occafions an increased action of that living power, which every organized body, fufceptible of ftimulus, naturally poffeffes; and which is fimilar to a blufh, being a momentary diftention of the smallest veffels, or that ftate of them, which immediately precedes the Motion flightest inflammation. thus begun, the veffels, furround- Now every feed of a plant is, in proper circumstances, which If, Every feed of a vegetable and every egg of an animal, hitherto examined, are in structure effentially the fame. To grow, that is to nourish itfelf by changing a foreign matter into its own fubftance, and to continue its kind, is the end and aim of every living organized body. Let us fee how far the feed of a vegetable is well adapted to effect these important purposes. The Windfor bean, from its fize and fhape will afford us a fair example. when fuch a bean is fully ripe, you cut through its membranes lengthwife, in the direction of the eye, hilum, or little fcar, it will naturally feparate into two halves. Thefe fmooth and equal parts of the bean are called feed-lobes by gardeners, and cotyledons by botanifts. Of feeds, that we use for food, they form the more farinaceous or nutritive part: thus in wheat, rye, and indian-corn, they form the meal, while the investing membranes form the bran. The most important part of the feed is the embryo; and the most important part of the em bryo is the corculum, or little heart, punctum vitæ, or fpeck of life; becaufe at this point in the hen's egg the first pulfation of life is difcovered; but in the feed of a plant there is no palpable warmth or visible motion. The whole feminal apparatus, contained within the external membrane When a hen's egg is alive, it is fit to be eaten; when killed, it foon becomes rotten; and fo of the feeds of vegetables. of the bean, namely the chalaza, albumen, and vitellus, parts correfponding with thofe found in the bird's egg, confpires to elicit the latent fpark of vegetative life, and to enliven and nourish the unborn plant. The plumala, which is the leaf of the plant in miniature, is that part of the embryo vegetable, that is hereafter to become the herb of the bean; whilft the inferiour part, called rofellum, creeps downwards, and becomes the root. The cotyledons or lobes of the bean taken collectively, without any difcrimination of chalaza, albumen, or vitellus, appear through a microscope, to be of a glandular Structure; and to have a regular fyftem of veffels, refembling the mefenteric veins in animals, and to run together, like them, in a few trunks, precifely at that point of the lobe, where the embryo grows to the cotyledons. Thefe cotyledons* conftitute the placenta of the feed, which affords a nutritive juice, refembling milk, for the fuftenance of the unborn plant. But when the tender vegetable is fo far advanced as to merit the name of a fœtal plant, thefe evanefcent lobes are converted into a pair of thick feedleaves, fo called, which compofe a fhield of defence, until the plant has fairly taken root in the earth ; then these two leaves $ The apricot exhibits this glandular ftructure ftill plainer than the bean. See Grew, plate 79. 80. 81. & 82. Botanists define cotyledons to be the lateral, bibulous, perishable lobe, or placenta of the feed, deftined to nourifh the corculum, and then to fall off. wither, drop off, and decay; and now the little erect plant, like the new-born infant, depends on a new principle for its future existence. From what has been faid, it is apparent, that a fecundated feed, though kept feveral years, is not a dead fubftance, like a pebble or pearl,* but a body regularly organized, and arranged into a fyftem of veffels, glands, and membranes; and that it is moreover alive, or at least in a flate, or fitnefs to be acted upon by certain external agents, which agents are FIRE, AIR, and WATER. We neglected to mention,. that there is a fmall quantity of vital air in a kind of fack or bladder at the big end of every bird's egg; and we prefume, there is a portion of the fame fluid in every feed. It appears alfo, that the most important, nay the effential part of that organized body, denominated a feed, is the embryo; for it is that alone which grows into a new plant, forming a new progeny. It likewife appears, that all the other parts of the feed are fubfervient to this, and are employed chiefly in converting the farina, or mealy fubftance of the feed, into a lactefcent fluidt, which is conveyed by the lactiferous veffels to the embryo for its nourishment, which, like the infantile animal, is fupplied with milk, until it can stand alone on the ground. Although nature has establish Indian corn has vegetated after keeping it upwards of feventy years. This milk is remarkable in Qatt; cut before they are fully ripened. pearance. ed a marked uniformity in the internal ftructure of feeds, fhe nevertheless difplays an aftonishing variety in their external apNeither mathematician nor painter can convey adequate ideas of their different fhapes and various colours. Some fhine like gold, and like filver; whilst others appear like little balls of fire. It is remarkable, that feeds are feldom of the fame colour with the flower, which produced them. Seeds of a deep green are rare; blue ftill more uncommon. Befide the effential parts, already defcribed, there are certain acceffory parts, which, whilft they add to the beauty of feeds, ferve important purposes in their migration; fuch, for example, are the feathery crowns, or aigrettes, which ferve as wings to waft them to a distance, as in Dandelion, Lettuce, and Thiftle. Who, walking the fields, has not obferved, Wide o'er the thifily lawn, as fwells the breeze, A whit'ning shower of vegetable down If feeds are diverfified in fhape $ Thomfon. Gartner, an accurate and laborious German botanift, has written most elaborately on feeds. Many curious and judicious extracts from his work, entitled "De Fructibus & feminibus Plantarum," may be seen in Dr. S. Barton's Elements of Botany, between p. 200 and 260. 1 Air and water are abfolutely Besides air and water, to which we may add fire, animals stand in need of aliment, or food taken by the mouth, which is afterwards digefted in the ftomach, forming there a milky liquor, called chyle. Food, or aliment is equally neceffary to the life and growth of vegetables. The conftituent parts of the chyle of animals are, waterfugar-mucilage--oil-carbonphofphorus and calcareous earth.* Sap-juitet, which is the chyle of vegetables, confifts, in like manner, of water-fugar--mucilage oil-carbon-phosphorus and calcareous earth. Striking as the analogy is between the aliment of animals and vegetables, the nutritive procefs differs widely in each. The animal has a warm receptacle, or ftomach, of about 98 degrees of heat, with a due quantity of water, and a peculiar compound motion; whereas the plant has no fuch receptacle, or any other stomach than the cold fluggish earth of about 53 degrees of heat. The poffeffion of a STOMACH lays the difcriminating line be * Calcareous earths are mark of all forts, limestone, chalk, marble, plaister of Paris, and all earths, formed from the bodies of animals, especially the hell of fish......Fordyce. + Darwin. tween the animal and vegetable king dom. All other diftinctions fail us. Sap-juice, or chyle of vegetables, is abforbed from the earth by the roots of plants; and from this juice, farther elaborated, refined and exalted, are formed all the various fluids in the stem, leaf, flower, fruit or feed of the plant. Some plants can extract, or compose these fubftances of water and air alone; yet we find by experiment, that fome materials contribute more to the production of this vegetable chyle than others.* Let us now inquire what the materials are that afford the food of plants. The fubject is important; for if we can difcover the appropriate aliment of any particular family of plants, we fhall be able to increafe their fize with as much certainty, as a farmer fattens his cattle by giving them corn. It is known from experiment, that a plant will grow in fand alone, moistened with water, purified by diftillation from all earthy particles, and in the pureft air. A plant will grow better in a mixture of fand and clay, in which the tenacity is adapted to the pufhing power of its roots, than in fand alone; and it will grow better, if a proper quantity of water be applied. But with both these advantages it will not flourish fo well as in a rich foil.t If in a proper mixture of fand and clay a plant be duly fupplied with water, it will grow better than in the fame mixture, expofed to the weather, and the chances See Darwin's Phytologia, Sect. X. +Fordyce's Elements of Agriculture and Vegetation. Vol. I. No. 10. Lü of being too moift or too dry; but it will grow ftill better in a rich foil. There is, therefore, in a rich foil, SOMETHING independent of texture, or the retention of water, which contributes to the flourishing of plants.* Some, from obferving the fertility after the ground was divided by the plough, have imagined that earth was the food of plants. To this opinion fucceeded another equally erroneous, viz. that water was their aliment, when in fact it is only the vehicle of their nourishment. The upper ftratum of earth, or garden mould, contains fome articles that are foluble in water, and fome that are not. Thofe which are infoluble in water are fand, clay, calcareous earth, magnesia, earth of allum, calces of metals, particularly iron, and the fibres of vegetables. These cannot enter the veffels of the roots of plants, but they may contribute to the production of fubstances that are foluble in water.f Subftances found in mould, that are foluble in water, are мUCILAGE, nitrous ammoniac, nitrous Selenities, common ammoniac, and fixed ammoniac.f. We find all thefe falts in the juice of vegetables; a proof that they pafs into the plant along with water. From numerous experiments it appears that a mucilage, produced by the decompofition of vegetable and animal recrements, conftitutes the aliment of vegetables. It is formed from stable manure; from dew; or from rain-water * Fordyce's Elements of Agriculture and Vegetation. + Fordyce, 450 putrified, as well as from dead But animals and vegetables. mucilaginous juices are of two kinds. One, when diffolved in water, forms a fort of jelly, and is an immediate aliment; the other forms a gummy, or facharine liquid, and must putify before it becomes a manure.† To reconcile the doctrine, that falt is the active principle in manures, it fhould be remembered, that putrefaction has two stages; that the first converts animal and vegetable fubftances into a mucilage, and the fecond converts that mucilage into one or more fpecies of falt. As mucilaginous fubftances were known to invigorate roots, by affording them good nourishment, it was natural for agriculturalifts, not enlightened by chemiftry, to infer, that fteeping feeds in mucilaginous, or oleaginous liquors, would increase their powers of vegetation, especially if a portion of nitre, common falt and lime were added. This opinion prevailed among the ancients, and is recommended by Lord Bacon.‡ A belief in the efficacy of fructifying liquors still prevails in many parts of Europe, although Dubamel in France, and Hunter in England, have expofed their futility. Dr. Hunter affures us, that he fprouted all kinds of grain in a variety of "fceps," and always found, that the rad + Fordyce. Sylva Sylvarum, art. accelleration of germination. Dr. A. Hunter, an eminent physician and venerable philofopher, at the city of York in England; author of several admirable georgical effays, and editor of Evlyn's Sylvia. water. icle and germ never appeared so that the radicle and germ, pro- If what we have before faid of the office of the feed lobes be just, that the farina, or meal, of which they are compofed, is converted into milk, that it ferves to nourish the infantile plant until its roots are large enough to imbibe mucilaginous food from the earth, it fol lows, that the vegetative powers of feed will be in proportion to the quantity of their mealy fubftance. If fo, then it will remain an establifhed truth, that plump feeds, placed at a juft depth, in a good foil, and at a proper feason, will never disappoint the gardener. From the preceding doctrine it alfo follows, that manures are of One adds nourishtwo kinds. ment to the foil, fuch as all ani |