174 
MORPHOLOGY OF MEMBERS. 
endogenous origin (Fig. 128, K K')] they are developed out of a cell in the interior of 
the tissue of the stem near to the growing point, and afterwards break through the base 
of the older leaf-sheaths. In some Jungermannieae the normal terminal branching of 
the stem takes place partially or entirely by endogenous formation of shoots ^. 
With these exceptions all normal lateral branches produced at the cone of growth 
of the bud or in its neighbourhood are, like the leaves, exogenous. 
(f) The lateral branches which arise normally below the growing apex of a mother- 
shoot are always produced in acropetal order, like the leaves, with which they exhibit 
various relationships as to position, age, and number. 
(a) The numerical relationship of the lateral branches to the leaves formed on 
the same axis is variable. If the number is unequal, a greater number of leaves 
than of branchlets usually arises on the same axis ; in Muscinese, Ferns, Rhizocarpeae. 
Cycadeae, and Coniferae a much larger number. A branchlet may arise when a de- 
finite number of leaves has been formed, as in many Muscineae and some Ferns, or 
the formation of a branchlet results when the increase in length of the primary axis 
and the formation of its leaves ceases for a time and is subsequently renewed, as 
in Abies. When the leaves stand in whorls, the number of the lateral branches 
may be equal to that of the members of the whorl, as in Equisetaceae, or smaller, as 
in Gharaceae. It is unusual for the number of branchlets to be larger than that of 
the leaves, but this occurs in some Angiosperms, where two or more lateral buds often 
arise side by side above a leaf (Fig. 130), or one above another, as in Aristolochia Sipho, 
Gleditschia, &c. In most Angiosperms the number of the lateral branchlets (with the 
exception of the flower-shoots) is, at first, the same as that of the leaves ; but usually 
only a much smaller number continue to develope. 
(/3) The relationship in position and origin of leaves and branches is constant in each 
species and often in a whole class of plants. The lateral branches arise below the leaves 
(according to the acute investigations of Leitgeb probably in all Mosses, as well as in 
^ [See Leitgeb, Bot. Zeit., 1872.] 
2 Leitgeb, Beiträge zur Entwickelungsgeschichte der Pflanzenorgane, in Sitzungsber. der kais. 
Fig. 129.— Longitudinal section through the apical 
region of a branch of Clematis apiifolia ; s apex of the 
stem ; d b leaves ; the first traces of spiral vessels, 
bending out uninterruptedly from the stem into the leaves. 
Fig. 130.— Bulb o{ Miiscari botryoides ; one of the 
lower bulb-scales is thrown back, in order to show the 
numerous buds standing side by side in its axil. 
