BUD, in botany, the embryo or rudiment of a plant, growing on the stems and branches of trees, and covered with scales, or with a resinous varnish, to protect it from the winter cold, and from the depredation of insects.—Buds proceed from the extremities of the young shoots, and along the branches, sometimes single, sometimes two by two, either opposite or alternate, and sometimes collected in greater numbers. In general, we may distinguish three kinds of buds: the leaf-bud, the flower-bud, and that containing both in one covering. The first species contains the rudiments of several leaves, which are variously folded over each other, and surrounded by scales. The second species, or flower-bud, contains the rudiments of one or several flowers, folded and covered in a similar manner. This bud is called by Pliny oculus gemmæ, or the eye of the bud, and is employed in that species of grafting, called inoculation. The third sort, which is the most common of any, produces both flowers and leaves. Buds, together with bulbs, which are a species of buds, generally seated on, or near the root, are very properly called by Linnæus hybernacula, a term signifying the winter-quarters of the embryon shoot.
As plants are supposed to bear a striking analogy to animals, they may, not improperly, be reckoned both viviparous and oviparous; in which view, seeds may be considered as vegetable eggs; buds, as living fœtus's, or infant plants, which renew the species as certainly as the seed.
As each bud contains in itself the rudiments of a plant, and would, if separated from its parent vegetable, become in all respect s similar to it, Linnæus, to shew the wonderful fertility of Nature, has made a calculation, from which it appears, that in a trunk scarce exceeding a span in breadth, no less than ten thousand buds may be produced. How great then must be the number of plants, which are capable of being raised from one large tree!—See the article Leaves.
Flower-buds of many trees, says Dr. Darwin, arise immediately from the terminating shoots or spurs of the preceding year, and are either accompanied with leaf buds or separately, as in apple and pear-trees. Others proceed from the shoots of the present year, alternately with leaf-buds, as those of vines, and form the third or fourth buds of the new shoots. They differ from leaf-buds, because they perish when their seeds are ripe, without producing any addition to the tree; the leaf-buds, on the contrary, decay in autumn, and their caudexes are then gradually converted into alburnum, or sap-wood; over which the new leaf-buds shoot forth their caudexes and radicles, or insert them into it, and gradually fabricate the new bark and root fibres.
Some of the disciples of Linnæus are of opinion, that about Midsummer leaf-buds may be changed into flower-buds, or flower-buds info leaf-buds; and this may be effected even after the vegetable embryons are generated, by weakening or strengthening the growth of the last year's buds. Hence, if some inches of a branch be lopped off at Midsummer, which is sometimes done by unskilful gardeners, the remaining buds on that branch will become more vigorous, and produce leaf-buds instead of flower-buds. But the contrary effect will take place, if a vigorous branch of a wall-tree be bent beneath the horizon, so as to impede the generation of new caudexes.