112 EMBRYO-BUDS.—ACCESSORY BUDS. 
buds differ from those commonly produced in the axils of leaves, 
or at least from those which remain dormant during the winter, 
in being smaller, and having no external protective organs or 
scales. 
Embryo-Buds.—In some trees the adventitious buds, instead 
of being developed on the outside of the stem or branch, are 
enclosed in the bark ; such have been called embryo-buds or 
embryo-nodules. They may be readily observed in the bark of 
certain trees, such as the Cork-oak, the Beech, and the Cedar of 
Lebanon, in which they produce externally little swellings, 
which, when examined, are found to be owing to the presence 
of these nodules, which have a more or less irregular ovoid ( fig. 
220) or spheroidal form, and woody texture. Upon making a 
transverse or vertical section of one of them (fig. 221), we 
observe a central pith surrounded by a variable number of 
concentric rings of wood according to its age, as in the wood 
of ordinary trees, and traversed by medullary rays ; in fact, it 
has all the structural parts found in the branch or trunk 
Fie. 220. 
Fig. 220. Embryo-bud or embryo-nodule of the Cedar.— Fig. 221. A vertical 
section of the same surrounded by the bark. 
of a Dicotyledonous tree. In the course of their develop- 
raent, these embryo-buds frequently reach the wood, with the 
growth of which they then become confounded, and thus form 
what are called knobs. In other cases a number of nodules 
raeeting together on the surface form an excrescence. That such 
nodules are analogous to buds is further proved by the fact of 
their sometimes producing a short branch from their summit, 
as in the Cedar of Lebanon and Olive. Those of the latter 
plant, under the name of Uovili, are really employed for its 
propagation. 
3. Accessory Buds.—The third cause of irregularity in the 
distribution and appearance of branches arises from the multi- 
plication of buds in the axils of leaves. Thus instead of one 
bud, we have in rare cases two, three, or more, thus situated 
(figs. 222-224) ; such are called accessory buds. These buds 
may be either placed one above the other, or side by side. 
Thus, in certain Willows, Poplars, and Maples, we have three 
buds placed side by side (fig. 222, a), which frequently give rise 
