UNDERGROUND STEMS. &9 
bud surrounded by more or less thickened scale-leaves. It 
serves the same purpose as the tuber, being chiefly a means 
of reproduction, but its reserve of nutriment is stored up chiefly 
in its scales. The Onion, Lily, &c., are familiar examples of 
bulbs. The transition stage between the bulb and the crhi- 
zome is seen in such solid bulbs (or corms*) as occur in 
Crocus and Gladiolus. In some plants—e.g., the Tiger Lily— 
the upper axillary buds or branches are normally developed 
as small bulbs, or bulbils, which drop off the parent plant in 
autumn, and gernunate at once if the soil be damp., 
-* Gr. kormos, a log or trunk. - 
