OUTLINE OF STRUCTURAL BOTANY 9 
selves bear leaves and other buds. When a bud is formed not 
terminal nor at a leaf axil it is an evtra awillary bud, or if in 
irregular order or at intermediate points, it is an adventive bud. 
The leaves usually arise from the stem in a certain fixed order, 
depending upon the species of plant, or the order of arrangement 
governed by a general law. In case of the presence of adventive 
buds or branches the orderly disposition of the leaves may be mate- 
rially disturbed. 
The points, or more exactly, the transverse 
planes, marking the insertion of the leaves are 
called nodes. These nodes are very clearly 
shown in the stems of grasses. The space com- 
prised between two successive nodes is an inter- 
node (Fig. 11). 
Upon the relative positions of axillary and 
terminal buds depend the divisions of the stem. 
A true bifurcation or forking from exactly op- 
posite buds is rare, especially in case of the 
higher plants, but a false bifurcation from buds 
situated in close proximity is much more com- 
eg ae Fic. 11 — Diagram 
Naturally the character of the divisions or indicating the  rela- 
bifurcations will determine the general form or tne bade ose 
port of the plant. If the terminal bud con- **7°¢es 
tinues to hold a considerable lead, the lateral buds sending out 
branches in their order the plant will assume a comparatively 
regular spire-top form such as we observe in case of the fir tree. 
But if a bud close to the terminal bud sends out a branch about 
equalling the latter and if the process is repeated indefinitely we 
have a widely branching stem, the rounded or flat top, such as is 
shown by the apple tree. 
The stem may be cylindric, as it is in many grasses, triangular 
as in some sedges, fluted, quadrangular or flattened. 
From the stem may arise imperfectly developed branches, woody 
and sharp, which are spines or thorns, these differ from the more 
superficial prickles, such as are found on the stem of the rose and 
many other plants, and which arise entirely from the bark. The 
stem is also modified to form tendrils, as we find them on the vine 
of the grape, though some tendrils are modified leaf-forms, as we 
find them in many species of the pea family, as well as in some 
other plants. 
