De I. VNER VEW D Forest Trees of the Pacific Slope

FOREST TREES OF THE PACIFIC SLOPE. 99
Best stands on flats, gentle slopes, heads of moist valleys, or in sheltered ravines
(below Crater Lake in Cascades of southern Oregon). Decidedly prefers north exposures,
doubtless on account of less heat and greater soil moisture there. Exposed high slopes
least favorable to best growth ; although often abundant there, it is usually stunted.
Commonly in limited pure stands and In mixture. At north, with Sitka spruce, western
hemlock, and alpine fir. Southward, at high altitudes, with white-bark pine, alpine fir,
Lyall larch, Engelimnn spruce, while grand fir, lodgepole and western white pines are
also occasional associates at lower elevations. Large pure stands are uncommon, but
rather extensive forests with 85 per cent of hemlock are occasional. Pure patches are
frequent on north slopes. In southern Alaska and British Columbia, with spruce, firs,
poplars, and birches. At high altitudes in California, often in groups with patches
of white-bark pine; lower, commonly with California red fir and lodgepole and western
white pines.
CLIMATIC CONDITIONS.-Endures severe alpine climate. Daily and seasonal ranges
of temperature great, owing to intense sunlight and rapid radiation of heat at night.
Rarity of air, together with frequent high winds, cause rapid transpiration, which is
modified somewhat by increased humidity due to low air temperature. Precipitation,
large; chiefly snow, which often buries trees. Snow comes early and stays late; melting
alowly, it supplies moisture throughout the short growing season. Rains are rather frequent
in spring and fall, but summers are usually hot and dry, especially on south
exposures.
TOLERANCE.-Very tolerant; excepting western hemlock, surpassing all associates in
shade endurance. Its dense shade, almost excluding light from ground, usually prevents
growth of seedlings, even its own, which appear to require more light than the heavy
shade of mother trees affords, but which thrive under lodgepole pine, fir, etc. Seedlings
and saplings bear long suppression, and rarely die under it. Trunks are not cleared
readily, even in dense stands; dead branches usually persist or leave short stubs which
form loose knots in timber.
REPaODUCTION.-Prolific seeder, producing cones when about 20 years old; seed is
borne annually, but not every year is a good seed year. Seed has only moderate rate of
germination, and its vitality is rather transient. With sufficient moisture, seed germinates
on both humus and mineral soils, but apparently better on latter. Seedlings
grow better in moderate shade and moist humous soil than in full light.
PSEUDOTSUGA. FALSE HEMLOCKS.
The generic name of the false hemlocks indicates a relationship to the hemlocks,
which they resemble in the distinctly formed leaf sterns and in the habit
and Character of their cones. The resin vesicles of hemlock seeds are, however,
absent from the seeds of Pseudotsugas. The latter have small resinpockets,
or " blisters," in the bark of young trunks and branches, in this respect
being similar to the firs. Woodsmen and lumbermen know them as " varieties "
of " fir " or " spruce," and even as " pines." Properly they should not be called
firs, from which they differ greatly in the character of their wood, foliage, and
cones. The superficial resemblance of the wood of these trees to pine is a
popular reason for calling them pines, but it is a perversion of the name, for in
all respects the pines are totally different trees.
False hemlocks are evergreen trees with dense, soft, flat leaves. Their
branches, growing in irregular circles, form with their many side-branches wide,
fan-like, densely foliaged sprays. The rough, very thick-barked trunks are tall
and massive, and taper slowly. They have broadly pyramidal crowns, which in
young trees extend to the ground. The flat, bluntish leaves, attached by distinct
stems, are spirally and singly arranged on the branches. They appear often
to grow mainly from two opposite sides and from the top of the branch; but
lower leaves bend upward toward each side of the branch by a twist in their
stems. Leaves of a season's growth remain on the tree about five or eight
years. In cross-section the leaves of our species show two resin-ducts on the
under margin near the edges of the leaves. Flowers of two sexes are borne
singly on branchliets, formed the previous year, on different parts of the same
tree. The female flowers are bristly, scaly bodies, developing into cones with