r slopes of the dividing
ridges the forest becomes more open and the trees are smaller. Salal,
Oregon grape, and huckleberry bushes take the place of the taller
undergrowth of the valleys. Up to 3,000 feet the Douglas fir and the
hemlock still are the dominant species. Above this altitude new species
are found intermingled with the trees typical of the lowland, but
forming a distinct forest type. The noble and amabilis fir appear,
sometimes growing in pure stands, but more often associated with the
Douglas fir and western hemlock at the lower limits of the type, and
with alpine fir and mountain hemlock at the upper limit.

Nearly all the trees of this type have deep and wide-spreading roots
which serve to hold in place the surface deposit of volcanic pumice
which covers the slopes of the mountain. Evidence afforded by the after
effects of forest fires in other parts of the Cascades indicates that
the destruction of the forest on the mountain sides is followed by
erosion. Heavy rains and the melting of the upper snow banks by warm
Chinook winds combine to produce a surface run-off that denudes the
steeper declivities down to the underlying bedrock.

At elevations above 4,500 feet the lowland trees have disappeared
entirely. Subalpine species adapted to withstand the burden of deep snow
take their place. Mountain hemlock, alpine fir, and Engelmann spruce
grow singly and in scattered groups or form open groves alternating with
grassy parks and rocky ridges. The symmetrical outline of the slender
pyramidal crowns and rapidly tapering trunks of the spruce and alpine
fir trees that stand singly on the greensward of the open parks bring to
mind the closely trimmed cultivated evergreens that adorn city parks and
lawns. Their lower branches reach the ground and the tops terminate in
slender upright spires.

As timber line is approached tree growth is confined to dwarfed and
flattened mountain hemlocks, alpine firs, and the white-bark pines
firmly rooted among the crevices of the rocks.

The extreme limit of tree growth on Mount Rainier is 7,600 feet above
sea level. There is no well-defined timber line. Scattered clumps of low
stunted trees occur up to 7,000 feet. A few very small and flattened
mountain hemlocks grow above this elevation. A very large part of the
area above 4,500 feet consists of glaciers, talus slopes, barren rocky
peaks, and open parks. Basins at the heads of canyons in the high
mountains are usually treel