18 PLAN OF VEGETATION. 
CHAPTER II. 
PLAN OF VEGETATION.—ELEMENTARY ORGANS. 
18. Tue earliest and simplest state of the plant is an embryo 
contained inaseed. ‘This consists essentially of two parts, the 
radicle and plumule; the former about to be developed into the 
root, the latter into the ascending plant with its appendages. 
19. As soon as the process of germination commences, the 
radicle begins to extend itself downwards in the direction of the 
earth’s centre, constantly avoiding the air and the light, forming 
the descending axis, or root. The plumule, taking the opposite 
direction, extends itself upwards, always seeking the light, and 
expanding itself, to the utmost extent of its power, to the influ- 
ence of the atmosphere. This constitutes the ascending azts, or 
trunk, around which the leaves and their modifications are 
arranged. 
20. At the commencement of its growth, the ascending axis 
is merely a bud, that is, a growing point, enveloped in rudimen- 
tary leaves, or scales, for its protection. As this growing point 
advances, the enveloping scales expand into leaves below, while 
new ones are constantly appearing, in succession, above. Thus 
the axis is always terminated by a bud. 
21. By this process the axis is elongated, simply i in one direc- 
tion. But, besides this, there is also a bud (or buds), either 
visible, or in a rudimentary state, formed in the axil of each 
leaf. 
a. These axillary buds are generally visible, either before or after the leaf has 
fallen. In some plants, however, they seldom appear; but their existence is 
inferred from the fact, that even in such cases, they are occasionally developed in 
extraordinary circumstances. 
22. Each bud is a distinct individual, capable of an independ- 
ent existence, in favorable circumstances, although severed from 
the parent stock. 
a. The common practice of propagation by layers, offsets, engrafting, and 
budding, is both a result and a proof of this principle. A plant may be, and 
