6 BULLETIN 460, V. S. DEPAETMEXT OF AGRICULTURE. 



denser (PL I, a) than that on trees in protected places or in close 

 stands (PL II). A cross section of the leaf shows one or two resin 

 ducts centrally situated near the border (back of leaf). 



The cones are matured at the end of the second summer, usually 

 by the first of September. They shed their seed soon afterward and 

 fall from the trees within a few months. Mature cones (PL I, b) 

 vary in length from about 6 to 10 inches: occasionally they are 

 slightly longer or shorter. Before the mature cones become 

 weathered by exposure the tips of the scales are red-brown or yellow- 

 brown, the inner portion of the scales being a deep red. The seeds 

 (PL I, c, d) are reddish brown, with small blackish spots. The seed- 

 leaves vary in number from 6 to 9 (PL II, a. b). 



The wood of western white pine is soft and of very light weight, 

 a cubic foot of dry wood weighing about 24 pounds. The sapwood 

 is nearly white and the heartwood is pale brown. The wood is very 

 similar in appearance and in its working qualities to the wood of 

 the eastern white pine (Pinus strohus), for which it is now exten- 

 sively substituted. 



OCCURRENCE AND HABITS. 



i 



Western white pine is not confined to any definite type of locality, 

 but it occurs at an elevation of from about 2,000 in moist valleys, 

 where it grows largest, to about 7,000 feet in dry, exposed, subalpine 

 regions, where the trees are much smaller (Map No. 1) . It is adapted 

 to a variety of soils. The best growth, however, occurs where they 

 are deep and porous. Regionally, the greatest development of west- 

 ern white pine is in northern Idaho and in adjacent parts of north- 

 western Montana, on gentle north slopes and flats. Lodgepole pine, 

 Englemann spruce, western larch, western red cedar, alpine fir, grand 

 fir, alpine hemlock, and western yew are variously associated with it 

 in different parts of its range. 



Western white pine endures considerable shade for a relatively long 

 period during its seedling and later young growth, after which it 

 requires abundant top light for its best development. Saplings or 

 pole forms of the tree do not recover and grow well after they have 

 been long suppressed by the shade of older trees. 



This pine is not a prolific seeder. It bears cones only when about 

 from 40 to 60 years old and at irregular- intervals of about two years. 

 As a rule, it reproduces itself sparingly. Seed germinates poorly on 

 heavy humus, unless the latter is thoroughly and constantly moist; 

 the best germination occurs on exposed, moist, mineral soil. 



LONGEVITY. 



Western white pine is a long-lived tree, attaining an age of from 

 200 to 500 years. 



