The Two-Leaved Pine (Pinus contorta, var. Murrayana), above the Silver Fir zone, forms the bulk of the alpine forests up to a height of from 8000 to 9500 feet above the sea, growing in beautiful order on moraines scarcely changed as yet by post-glacial weathering. Compared with the giants of the lower regions this is a small tree, seldom exceeding a height of eighty or ninety feet. The largest I ever measured was ninety feet high and a little over six feet in diameter. The average height of mature trees throughout the entire belt is probably not far from fifty or sixty feet with a diameter of two feet. It is a well-proportioned, rather handsome tree with grayish-brown bark and crooked, much-divided branches which cover the greater part of the trunk, but not so densely as to prevent it being seen. The lower limbs, like those of most other conifers that grow in snowy regions, curve downward, gradually take a horizontal position about half-way up the trunk, then aspire more and more toward the summit. The short, rigid needles in fascicles of two are arranged in comparatively long cylindrical tassels at the ends of the tough up-curving branches. The cones are about two inches long, growing in clusters among the needles without any striking effect except while very young, when the flowers are of a vivid crimson color and the whole tree appears to be dotted with brilliant flowers. The staminate flowers are still more showy on account of their great abundance, often giving a reddish-yellow tinge to the whole mass of foliage and filling the air with pollen. No other pine on the Range is so regularly planted as this one, covering moraines that extend along the sides of the high rocky valleys for miles without interruption. The thin bark is streaked and sprinkled with resin as though it had been showered upon the forest like rain.
Therefore this tree more than any other is subject to destruction by fire. During strong winds extensive forests are destroyed, the flames leaping from tree to tree in continuous belts that go surging and racing onward above the bending wood like prairie-grass fires. During the calm season of Indian summer the fire creeps quietly along the ground, feeding on the needles and cones; arriving at the foot of a tree, the resiny bark is ignited and the heated air ascends in a swift current, increasing in velocity and dragging the flames upward. Then the leaves catch forming an immense column of fire, beautifully spired on the edges and tinted a rose-purple hue. It rushes aloft thirty or forty feet above the top of the tree, forming a grand spectacle, especially at night. It lasts, however, only a few seconds, vanishing with magical rapidity, to be succeeded by others along the fire-line at irregular intervals, tree after tree, upflashing and darting, leaving the trunks and branches scarcely scarred. The heat, however, is sufficient to kill the tree and in a few years the bark shrivels and falls off. Forests miles in extent are thus killed and left standing, with the branches on, but peeled and rigid, appearing gray in the distance like misty clouds. Later the branches drop off, leaving a forest of bleached spars. At length the roots decay and the forlorn gray trunks are blown down during some storm and piled one upon another, encumbering the ground until, dry and seasoned, they are consumed by another fire and leave the ground ready for a fresh crop.
In sheltered lake-hollows, on beds of alluvium, this pine varies so far from the common form that frequently it could be taken for a distinct species, growing in damp sods like grasses from forty to eighty feet high, bending all together to the breeze and whirling in eddying gusts more lively than any other tree in the woods. I frequently found specimens fifty feet high less than five inches in diameter. Being so slender and at the same time clad with leafy boughs, it is often bent and weighed down to the ground when laden with soft snow; thus forming fine ornamental arches, many of them to last until the melting of the snow in the spring.