THE BUD 
4i 
is covered by the young leaves folded over it ; if they be 
removed (as is easily done in Hippuris) the exposed apex 
of the stem is seen, under the microscope, to consist of a 
convex mass of embryonic tissue, on which lateral swellings 
arise exogenously (i.e. from the external layers) in acropetal 
succession (cf. Roots). At first all alike, these outgrowths 
ultimately differentiate into leaves and branches. Branches 
thus produced are termed lateral branches. Another type 
of branching is common in lower plants, viz. dichotomy, 
where the growing apex divides at the summit into two 
equal halves, but this is practically unknown in the higher 
plants. 
The bud is very important, and from the young and 
tender nature of its parts is very susceptible to injury. In 
tropical climates with plenty of moisture it may be injured 
by the intense radiation decomposing its chlorophyll, or by 
heavy rain. In hot sun or very dry places it is further liable 
to excessive evaporation. In temperate climates it is often 
exposed to snow, rain and cold, and many buds have to 
survive the winter. Against these dangers buds are protected 
in various ways, by the older leaves, by scales, hairs, wax, &c. 
(see Herbs, Trees, Xerophytes, &c. in Chap. III.). Buds 
are often detached to start growth on their own account 
(vegetative reproduction, see below). 
The arrangement of the leaves in the bud is called their 
vernation ; it is constant for each kind of plant, and is 
described in the same terms as that of the flower bud (see 
below, Aestivation). 
The Branches . At the growing apex of the stem 
exogenous outgrowths are formed, some of which usually 
develope into branches. A stem is rarely quite unbranched ; 
it usually branches in the flowering portion if not in the 
vegetative. If we leave the former out of account we may 
say that the stem is unbranched in most Palms and many 
other Monocotyledons, and in a few Dicotyledons. The 
branching is lateral, and commonly the position of the 
branches bears some definite relation to that of the leaves. 
In many ferns the branches appear on the leaf-bases, in 
Equisetum they are axillary {i.e. in the angles between 
leaves and stem), and the same is so generally the case in 
flowering plants (except Pistia, &c.), that the usual mode of 
