Bulb, in botany, a kind of large subterraneous bud, though sometimes appearing above ground, upon or near the root of certain herbaceous plants, which are therefore denominated bulbous. Linnaeus considers the bulb as the winter-quarters of the future vegetable; because every bulb contains, in miniature or embryo, a plant, in all respects similar to its parent ; so that many plants and trees may be propagated, with equal facility, by the bulbs or buds, as well as by the seeds.

The tender rudiments of the future vegetable, of which the bulb or bud is composed, are inclosed, and, during the severities of winter, defended against cold, and other external injuries, by a hard bark, or rind, which generally consists of a number of scales, placed over each other, like tiles, and fastened together by means of a tenacious, resinous, and frequently odoriferous substance. Thus defended, the buds remain upon different parts of the mother plant, till the ensuing spring.

Bulls are distinguished from buds, by this circumstance, that the former are generated on the broad caudex of the plant within the ground, or in contact with it, and immediately shoot down their roots into the earth ; whereas, buds are formed above the soil, on the long caudexes which constitute the filaments of the bark of trees, and shoot down new roots from the lowerend of those elongated trunks.

Dr. Darwin observes, that bulbs may be divided into leaf and flower-bulbs. When a tulip seed is sown, it produces a small plant the fust summer, which in the autumn thes, and leaves in its place one or more bulbs. These are leaf-bulbs, which, in the ensuing spring, rise into stronger plants than those of the first year, but no flowers are yet generated: in the autumn, these perish like the former, and leave, in their places, other leaf-bulbs, stronger, or more perfect, than their preceding parents. This succession continues for four or five years, till at length the bulb acquires a greater perfection or maturity, necessary for seminal generation, and produces in its place a large flower-bulb in the centre, with several small leaf-bulbs around it.

This successive formation of leaf-bulbs in bulbous-rooted plants, previous to the formation of a flower-bulb, is curiously analogous to the production of leaf-buds on many trees for several years, before the production of flower-buds : thus, apple-trees, raised from seeds, generate only leaf-buds for ten or twelve years, and afterwards annually produce both flower and leaf-buds. Hence it appears that the adherent lateral or paternal progeny, being the most simple and easy, is consequently the first mode of re-production ; and that the propagation by seed is not accomplished till the maturer age or more perfect state of the parent-bud.

Bulbous roots are said to be solid, when composed of one uniform lump of matter, as in the tulip ; tunicated or coated, when formed of a plurality of coats, surrounding-one another, as in the onion; squamous, or scaly, when composed of lesser scales, as in the lily ; jointed, as in the tuberous moschatel; duplicate, when there are only two bulbs to each plant, as in the crocus and saffron ; and aggregate, when there is a congeries of such roots to each.'

One of the most striking phae nomena in vegetable nature, is that of raising plants from their bulbs, without earth. Duhamel even raised small oak trees-, merely by water, in which he kept them eight years: they produced fine leaves every spring, and grew more rapidly during the two first year?, than if they had been planted in the best earth: an useful hint this to the cultivators of that noble tree!

As bulbs immersed in water produce roots, stem, and leaves, we might be induced to think, that the order of their growth, in these different parts, would be alike; but experience evinces the contrary. Duhamel cut off some of the largest hyacinth-roots, almost two ringers breadth from their ends; then placed the bulb on a bottle, in such a position, that the end of the cut root touched the water; and made a mark on the outside of the bottle, exactly opposite to the extremity of the root ; he likewise made marks corresponding to the ends of some entire roots. The latter continued growing, and soon extended beyond the mark of their former length ; but the ends of the cut roots remained stationary. This experiment clearly demonstrates, , that roots only grow at their end.