in phytology, the act whereby plants receive nourishment and growth.

The process of nature in the vegetation of plants is very accurately delivered by Malpighi: 'The egg or seed of the plant being excluded out of the ovary, called pod or husk, and requiring further fostering and brooding, is committed to the earth; which having received it into her fertile bosom, not only does the office of incubation by her own warm vapours and exhalation, joined with the heat of the sun, but by degrees supplies what the seed requires for its further growth; as abounding everywhere with canals and sinuses, wherein the dew and rain water, impregnated with fertile salts, glide, like the chyle and blood in the arteries, &c. of animals. This moisture meeting with a new-deposited seed, is percolated, or strained through the pores or pipes of the outer rind or husk, corresponding to the fecundines of the testicles, on the inside whereof lies one or more, commonly two, thick seminal leaves, answering to the placenta in women, and the cotyledons in brutes.

These seed-leaves consist of a great number of little vesicles, or bladders, with a tube corresponding to the navel-string in animals. In these vesicles is received the moisture of the earth, strained through the tine of the seed; which makes a slight fermentation with the proper juice before contained therein. This fermented liquor is conveyed by the umbilical vessel to the trunk of the little plant; and to the germ or bud which is contiguous thereto: upon which a vegetation and increase of the parts succeed.

Such is the procedure in the vegetation of plants; which the illustrious author exemplifies in a grain of wheat, as follows: The first day the grain is sown it grows a little turgid; and the fecundine, or husk, gapes a little in several places; and the body of the plant, being continued by the umbilical vessel to a conglobated leaf (which is called the pulp or flesh of the seed, and is what constitutes the flower) swells; by which means, not only the germ or sprout (which is to be the future stem) opens, and waxes green, but the roots begin to bunch out; whence the placenta, or seed-leaf, becoming loose, gapes. The second day, the fecundine or husk, being broke through, the stem, or top of the future straw, appears on the outside thereof, and grows upward by degrees; in the mean time, the seed-leaf guarding the roots becomes turgid with its vesicles, and puts forth a white down. And the leaf being pulled away, you see the roots of the plants bare; the future buds, leaves, and rest of the stalk, lying hid. Between the roots and the ascending stem the trunk of the plant is knit by the navel-knot to the flower-leaf, which is very moist, though it still retains its white colour and its natural taste. The third day, the pulp of the conglobated, or round leaf, becomes turgid with the juice which it received from the earth fermenting with its own.

Thus the plant increasing in bigness, and its bud or stem becoming taller, from whitish turns greenish; the lateral roots also break forth greenish and pyramidal from the gaping sheath, which adheres chiefly to the plant; and the lower root grows longer and hairy, with many fibres shooting out of the same.

Indeed there are hairy fibres hanging all along on all the roots, except on their tips; and these fibres are seen to wind about the saline particles of the soil, little lumps of earth, &c. like ivy; whence they grow curled. Above the lateral roots there now break out two other little ones.

The fourth day, the stem mounting upwards, makes a right angle with the seminal leaf: the last roots put forth more; and the other three growing larger, are clothed with more hairs, which strictly embrace the lumps of earth; and where they meet with any vacuity, unite into a kind of network.

From this time forward the root pushes with more regularity downward, and the stalk upward, than before. There is, however, this great difference in their growth, that the stalk and branches find no resistance to their shooting up, while the roots find a great deal to their shooting downward, by means of the solidity of the earth; whence the branches advance much faster and farther in their growth than the roots; and these last often finding the resistance of a tough earth unmountable, turn their course, and shoot almost horizontally.

From a number of experiments made by Mr Gough, and related by him in the fourth volume of the Manchester Transactions, it appears, that seeds will not vegetate without air; and that during their vegetation, they absorb oxygen, part of which they retain, and that carbonic acid is formed with the rest. These facts were ascertained in the following manner: He put several parcels of steeped peas and barley, at different times, into phials, which were left to stand for three or four minutes in spring water, of the heat of 46°, to reduce them to a known temperature. They were then securely corked, and removed into a room, the temperature of which was never less than 53°. After remaining from four to six days in this situation, they were again placed in the same spring water, and opened in an inverted position, care being taken that the barometer stood at the time nearly where it did at first. When a cork was thus drawn, a quantity of water rushed in immediately, more than was sufficient to fill the neck. The air being passed through lime water, contracted very sensibly, and precipitated the lime. The residuum, freed in this manner from carbonic acid, extinguished a lighted taper like water; and this it did repeatedly. He made one of these experiments with more attention than the rest, from which it appeared, that four ounces, one dram, forty grains, by measure, of atmospheric air, lost one-sixth of its original bulk, by being confined five days with one ounce of steeped barley. It is plain, from this experiment, that seeds in the act of vegetation take oxygen from the atmosphere, part of which they retain, and reject the rest charged with carbon. The substance of the seed-lobes is hereby changed, an additional quantity of oxygen being introduced into their composition; and a part of their carbon lost. This change, in the proportion of their alimentary principles, generates sugar, as is evident from the process of malting. But sugar and carbonic acid are more soluble in water than the farinaceous oxyd. They therefore combine with the humidity in the capillary tubes of the seed, and find a ready passage to the germ, the vegetative principle of which they call into action by a stimulus suited to its nature. A nutritious liquor being thus prepared by the decomposition of the seed-lobes, and distributed through the infant plant, its organs begin to exert their specific actions, by decomposing the nourishment conveyed to them, and forming new oxyds from the elementary principles of it, for the increase of the vessels and fibres; and in this manner the first stage of vegetation commences.

Mr Gough has ascertained, that a germ in the act of vegetation requires to be continually excited by the stimulus of oxygen; but that as soon as the seed lobes are exhausted, the young plant is in a state to derive its nutrition from the ground; and then (and not till then) it finds itself in a situation capable of making future advances, unassisted by the stimulus of respirable air.

The infant sprout at first suffers only a suspension of its energy from the absence of pure air; but if this necessary support be withheld too long, it perishes by the putrefactive fermentation.

The lively green which the stems and leaves of plants receive from the action of light, cannot be imparted to them, provided the energy of the vegetative principle in them be suspended: for after permitting a number of peas to produce both extremities of their sprouts in wet sand covered from the light by an earthen pot, Mr Gough placed five of them, on the 29th of April, in an inverted glass jar, containing azot confined by water; and three in another jar, in which a portion of common air was also inclosed by the same means. On the 30th the upper extremities of the sprouts of the parcel last mentioned were green; but though the experiment was prolonged to the 2d of May, those in the other glass did not exhibit any perceptible alteration in size or colour. Two of them were now placed in a glass filled with atmospheric air, where they were left unobserved to the 5th, at the end of which time the germs had vegetated considerably; the lower parts of them still remained white, but their opposite extremities had changed to their proper green. Hence it may be safely inferred, that greenness cannot be imparted to the sprouts of seeds without the joint action of light and oxygen; in which they are very different from the shoots that frequently proceed from mature plants, when excluded from the atmosphere: for, as these grow freely in close glass vessels, placed in a window, and containing water and azot, the parts which are recently produced continue to vegetate, in consequence of their connection with the parent stock, and acquire the colour in question without the affluence of respirable air. See Plant, Tree, Germination, Botany, &c.

VEGETATIVE soul, among philosophers, denotes that principle in plants by virtue of which they vegetate, or receive nourishment and grow. See the preceding article.