6 BULLETIN 460, U. S. DEPARTMENT 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 (PI. I, d) 
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 (PI. IT, a, d). 
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 strobus), for which it is now exten- 
sively substituted. | 
OCCURRENCE AND HABITS. 
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 een parts os its range. 
Western white pine andl considerable shode 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. 
