Pinus 



1003 



year ; symmetrical, or oblique with the scales larger on the outer side of the cone. 

 The exposed part of each scale in the unopened cone, known as the apophysis, is 

 thickened and shows the apex of the growth of the first year as a terminal or dorsal 

 protuberance or scar called the umbo, which is either unarmed or provided with a 

 sharp prickle or stout spine. The cones in most species open their scales when ripe, 

 allowing the seed to escape ; but in P. Cembra, P. pumila, and P. albicaulis the scales 

 are incapable of dehiscence, and the seeds are liberated by the attacks of squirrels and 

 other animals. In other species a large proportion of the cones remain on the 

 trees unopened for many years, the scales ultimately separating when scorched by 

 forest fires. Usually the cones fall through decay at the insertion of their peduncle ; 

 but in P. resinosa, P. ponderosa and P. palustris separation occurs near the base of 

 the cone, a few of the lower scales remaining attached by the stalk to the branch. 



Seeds, two on each scale, obovate, triangular or cylindrical ; wing embracing by 

 its rim-like base the sides and part of the upper surface of the seed, and either 

 separating freely from it as in the Hard Pines, or adhering closely and breaking off 

 from it irregularly as in P. Strobus and its allies. In certain species, the seeds of 

 which are edible and distributed by animals, the wing, no longer serving for flight, 

 is either reduced to a mere vestige only visible on the upper surface of the seed, as 

 in P. Cembra and its allies, or it is much shortened and reduced to a narrow lateral 

 rim, which usually remains on the scale when the seed falls, as in P. Pinea, P. 

 cembroides, P. Bungeana, and their allies. 



In germination the shell of the seed, from which the wing has usually fallen, is 

 raised as a hood on the top of the cotyledons,^ which vary from three to eighteen in 

 number and are usually triangular, flat, and green below, and keeled and marked 

 with stomata above, entire in margin, acute or mucronate at the apex. The young 

 stem elongating bears primordial leaves, in the axils of which the adult fascicled 

 leaves are usually produced in the second year. 



About eighty species of Pinus are known, distributed through the northern 

 hemisphere from the Arctic circle to Central America, the West Indies, Canary 

 Islands, Morocco, Algeria, Syria, Himalayas, Burmah, Philippine Islands, Sumatra, 

 and Borneo. Of these about fifty-two species are in cultivation, which may be 

 arranged as follows : — 



I. Haploxylon, Koehne, Deutsche Dendrologie, 28 (1893). Soft Pines.' 



Leaves with a single fibro- vascular bundle. Scale- leaves subtending the 

 leaf- clusters inserted on prominent bases, which are not decurrent on the 

 branchlets. Cones symmetrical, opening when ripe. Seed - wing present or 

 obsolete, not readily detachable from the seed. Cortex persistent on young 

 trees for many years. Walls of tracheids of medullary rays of the wood not 

 dentate. The wood is usually soft, close-grained, and light in colour ; sap wood 

 generally narrow. 



1 The number of cotyledons in each species is variable within narrow limits, and is stated by Dr. Masters \x^Jaum. Linn. 

 Soc. (Boi.) xxvii. 236 (1891). Cf. also Hill and de Fraine, in Ann. Bot. xxiii. 199 (1909). 



2 The shoots are always uninodal in the soft pines. 



