BULB n.
A spheroidal body growing from a plant either above or below the ground (usually below), which is strictly a bud, consisting of a cluster of partially developed leaves, and producing, as it grows, a stem above, and roots below, as in the onion, tulip, etc. It differs from a corm in not being solid.
BUR; BURR n. 2 definitions
Any rough or prickly envelope of the seeds of plants, whether a pericarp, a persistent calyx, or an involucre, as of the chestnut and burdock. Also, any weed which bears burs. Amongst rude burs and thistles. Milton. Bur and brake and brier. Tennyson.