40) NORTH AMERICAN FAUNA. [No. 16. 
These dwarf groves offer attractive shelters from wind and storm, 
and we usually camped among them when working the upper slopes. 
The tree is one of exceptional hardihood, and as it pushes on still 
farther into the realm of cold the trunks become completely prostrate 
and the branches hug the ground, forming among the rocks dense mats 
which sometimes rise a foot or two above the general level, but at their 
upper limit usually occupy depressions, or, if growing in the lee of a 
bowlder, crouch behind it and continue its surface level to the adjacent 
slope, as if trimmed to tit. Indeed, one is amazed at the way these 
uppermost pines avoid exposure by flattening themselves into the hol- 
lows, as if afraid to lift a finger above the general level. Their life isa 
perpetual struggle—not against competing plants, but against a hostile 
environment. In summer they are buffeted by the winds and pelted by 
sand and gravel; in spring they are swept and torn by the resistless 
avalanches, and in winter they are deeply buried under heavy banks of 
snow. The prostrate trunks in young and middle-aged healthy trees 
are completely concealed, often half covered by stones and pumice sand, 
and hidden by the density of their own branches and foliage; butin very 
old trees, and those injured by passing avalanches or laid bare by the 
washing away of protecting rocks during violent storms, the trunks are 
partly exposed and their extraordinary features may be easily examined. 
As arule they are not only naked, but the strongly twisted wood, 
gnarled, contorted, and, ironlike in firmness, has been eaten into by 
the sand blast till the knots and hardest parts stand out in prominent 
ridges. 
A little below timberline on the north side of Shasta, between North 
Gate and Shastina, is an extensive gently sloping pumice plain, strewn 
with fragments of gray shaly lava, and thickly spotted with rather 
-— = 
Fig. 22.—Pumice plain north side of Shasta, showing timberline mats of white-bark pines. 
large mats of pines, averaging 2 to 4 feet in height, which give a most 
curious aspect to the region (fig. 22). This area, which is abont a mile 
