2 GENUS PINTS 



Invisible or latent buds are present at the nodes and at the apex of dwarf shoots. The former are 

 the origin of the numerous shoots that cover the trunk and branches of P. rigida, leiophylla and a few 

 other species (fig. 10) . The latter develop into shoots in the centre of a leaf -fascicle (fig. 11) when the 

 branchlet, bearing the fascicle, has been injured. 



The size, color and form of buds, the presence of resin in quantity, etc., assist in the diagnosis of 

 species. Occasionally a peculiar bud, like that of P. palustris, may be recognized at once. 



THE BRANCHLET. Plate I, figs. 12-14. 



The branchlet, as here understood, is the whole of a season's growth from a single bud, and may 

 consist of a single internode (uninodal, fig. 12-a) or of two or more internodes (multinodal, fig. 13), 

 each internode being defined by a leafless base and a terminal node of buds. 



The spring-shoot is uninodal in all Soft Pines and in many Hard Pines, but, in P. taeda and its 

 allies and in species with serotinous cones, it is more or less prevalently multinodal. 



The uninodal spring-shoot may remain so throughout the growing season and become a uninodal 

 branchlet. Or a summer-shoot may appear on vigorous branches of any species with the result of 

 converting a uninodal spring-shoot into an imperfect multinodal branchlet. The summer-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 con- 

 dition prevents its employment for grouping species. For Pines are not sharply divided into multi- 

 nodal 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, how- 

 ever, 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, espe- 

 cially 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 mi- 

 nute hairs, etc., are often suggestions for determining species. 



THE SECONDARY LEAF. Plate II. 



Secondary leaves, the permanent foliage of Pines, are borne on dwarf-shoots in the axils of pri- 

 mary leaves. They form cylindrical fascicles, rarely monophyllous, prevalently of 2, 3 or 5 leaves, 

 occasionally of 4, 6, 7, or 8 leaves. The scales of the fascicle-bud elongate into a basal sheath, decid- 



