shoot may be recognized, during growth, by its green, not
scarious bracts and, at the end of the season, by the imperfect growth
of its wood and foliage (fig. 14).

The perfect multinodal branchlet is formed in the winter-bud (fig. 8-a)
and the spring-shoot is multinodal. It is gradually evolved among the
Hard Pines, where it may be absent, rare, frequent or prevalent,
according to the species. In fact there is, in Pinus, an evolutionary
tendency toward multinodal growth, with its beginnings in the
summer-shoot and its culmination in the multinodal winter-bud, most
prevalent among the serotinous Pines.

The multinodal shoot is never invariable in a species, but is rare,
common or prevalent. This condition prevents its employment for grouping
species. For Pines are not sharply divided into multinodal and uninodal
species, and no exact segregation of them, based on this difference, is
possible. In fact the character is unequally developed among closely
related species, such as P. palustris and caribaea. Both produce
multinodal shoots, but the former so rarely that it should be classed as
a uninodal species, while the latter is characteristically multinodal.
The multinodal spring-shoot, however, has a certain correlative value in
its relation to other evolutionary processes that are obvious in the
genus.

The length of the branchlet is much influenced by different soils and
climates. In species able to adapt themselves to great changes, the
length of the internode may vary from 50 cm. or more to 1 cm. or less.
In the latter case the branch is a series of very short leafless joints
terminated by a crowded penicillate tuft of leaves (fig. 12-b). Such a
growth may be seen on any species (ponderosa, albicaulis, resinosa,
etc.) that can survive exposure and poor nourishment.

The presence of wax, as a bloom on the branchlet, is associated with
trees in arid localities, especially Mexico, where it is very common.
With several species the character is inconstant, apparently dependent
on environment, and is a provision against too rapid transpiration.

The branchlet furnishes evidence of the section to which the species
belongs, for the bract-bases persist after the bracts have fallen away.
The color of the branchlet, its lustre, the presence of minute hairs,
etc., are often suggestions for determining species.

[Illustration: PLATE I. PRIMARY LEAF, BUD AND BRANCHLET]

THE SECONDARY LEAF. Plate II.

Secondary leaves, th