average of from 2,700 to 5,500 board feet. The largest Douglas firs
are sometimes over 400 years old and 60 to 70 inches in diameter. Such
trees when sound will produce over 8,000 feet of lumber.

The western red cedar has a shorter and more tapering trunk and its
volume in board feet is proportionally smaller. A tree 50 inches in
diameter and 175 feet high contains about 3,400 board feet.

The size of the trees decreases rapidly at higher elevations. In the
subalpine forest the annual growth is very small. At elevations of 6,000
feet the white-bark pine requires 200 years to attain a diameter of 10
or 12 inches. The annual rings are so close together that they can not
be distinguished without a magnifying glass.

DESCRIPTIONS OF SPECIES.

DOUGLAS FIR (PSEUDOTSUGA TAXIFOLIA).

The Douglas fir (figs. 2, 3, 4, and 5) is the best known and the most
important timber tree of western North America. It is found from
British Columbia southward to northern Mexico. The finest forests occur
in Oregon and Washington at low elevations. The Douglas fir is common in
the park up to 3,500 feet, sometimes in nearly pure stands, but more
often mixed with other species. It grows in all situations. In the
higher mountains it prefers warm southern exposures and is seldom found
on wind-swept ridges. It seeds annually, but most profusely at intervals
three or four years apart. The red squirrels gather and store large
quantities of the cones in order to provide a supply of the seeds for
their winter rations. The growth of the young tree is very rapid. As the
tree becomes older the rate of growth varies with the situation and the
character of the soil so that the size does not closely determine the
age of the tree.

[Illustration: FIG. 2.--Douglas fir (_Pseudotsuga taxifolia_).]

The Douglas fir is a long-lived tree, and specimens are occasionally
found 250 to 270 feet high and over 8 feet in diameter and between 400
and 500 years in age. It reaches its greatest height and most perfect
proportions in mature even-age stands growing on fairly moist
well-drained bench lands. Under these conditions it is a very tall and
beautiful tree. The trunk is straight, round, and free from branches for
two-thirds of its height and tapers gently to the crown. The dark-brown
deep-furrowed bark is 5 to 10 inches thick at the base of the tree.

The Douglas fir ranks first among the trees of the Pacific slope in
importance for the production of lumb