GROWTH BY THE STEM. 



31 



64. Bulbs are buds of a particular kind, larger 

 than common, containing an unusual quantity of se- 

 creted matter, and separable, spontaneously, from the 

 part which bears them. They are magazines in which 

 certain plants store up the nutritive matter collected 

 from the leaves. The identity of a bulb and a bud, 

 in all essential circumstances, is obvious, if the bud of 

 any tree {Jig. 4.) is compared with the bulbs of the 

 Tiger Lily {fig. 3.). 



55. As leaf-buds are thus the parents of wood, one 

 of the means of propagating the individual to which 

 they belong, the origin of branches, and consequently 

 the source of the developement of leaves themselves, 

 they may be considered the most important organs of 

 vegetation, so far as any one organ can be called Tnost 

 important where all are so mutually dependent the 

 one on the other, and so powerfully concur in main- 

 taining the system of vegetable life, that it is difficult 



