PINUS. 307 



In respect of branching, the Pines conform to the general law 

 observed throughout the Abie tin ere. 



The primary brandies are produced in pseudo-whorls, the lowermost of 

 which, even when the trees are standing alone, are gradually cast off with 

 advancing age ; when the trunk ceases to ascend there is usually an 

 irregular development of the topmost branches. The branchlets are 

 whorled and always continue upturned during their development, after 

 which they gradually assume a horizontal position. The foliage leaves 

 are mostly produced in definite numbers ; fascicles of two, three and five 

 are most common, but in Pinus monopliylla the leaves are mostly solitary 

 and terete ; in P. r/ntis, P. cembroides and one or two others, fascicles 

 of two and three occur regularly, and in P. Parryana fascicles of four 

 are most frequent. The shape of the leaves is determined by the number 

 in each fascicle ; where there are two they are semi-terete or plano- 

 convex ; where there are three, the ventral (inner) side is usually sharply 

 keeled and the dorsal (outer) side convex or nearly flat; and where there 

 are five they are regularly triangular in section. The stomata are mostly 

 disposed in longitudinal rows indicated by white lines and usually on the 

 inner or flat sides, but in P. Pinaster and its allies they occur on both 

 surfaces. The persistence of the leaves varies in the different species 

 from two to twenty years. 



The following diagnosis of the flowers and fruits is abridged from 

 Engelmamrs Ee vision of the " Genus Pinus." 



Flowers monoecious on different branches. Staniinate flowers either 

 crowded together into a kind of capitulum (head) or elongated into a 

 spike, cylindric or oval-cylindric, surrounded at the base by few or many 

 (three fifteen) involucral bracts. Anthers with an orbicular or sub- 

 orbicular connective bearing two anther cells. 



Ovuliferous flowers sub-terminal, sub-sessile or pedunculate, solitary or 

 in clusters of two five or more, composed of numerous scales of a two- 

 fold structure, the sporophyll (seed-scale) and bract, the former bearing 

 two pendulous ovules 011 the lower part .of the inner face and the latter 

 concealed and disappearing in the ripe cone. 



Cones maturing at the end of the second, rarely in the third season, 

 pendulous in some species, horizontal or erect in others ; in shape conical, 

 sub-globose or cylindric, often more or less oblique so that the scales 

 become unequal. Scales at first closely imbricated, the exposed part 

 more or less thickened (apophysis) and terminating in a blunt point or 

 rhomboidal swelling armed with a weak or strong prickle. Seeds obovate 

 or more or less triangular and compressed, winged, the wing sometimes 

 reduced to. a narrow rim. 



In most species the cones open their scales soon after maturity, drop 

 their seeds and then fall off; in others the open cones remain on the 

 trees for years after shedding their seeds, as in Pinus Sabiniana ; whilst in 

 others belonging to the Pinaster and Tsedse sections, the cones remain 

 closed on the trees for an indefinite period until opened by the heat 

 of a forest fire or an exceptionally hot season. 



The grouping of the species of Pinus into sections is not free from 

 difficulty. The older botanists used the number of leaves in a bundle 

 .as marks of sectional divisions, and neglecting all other characters 

 divided the Pines into three sections, the two-leaved, three-leaved and 



