274 BOTANICAL GAZETTE [APRIL 
be 59.24 in. On the eastern side of the Great Western Divide the 
precipitation falls rapidly, Truckee (5218 feet) having but 26.98 
in. (table C). 
Most of the annual precipitation in the high Sierra falls as 
snow and some astonishing totals are recorded from the Tahoe 
region. At Summit, in the winter of 1889-90, 776 in. of snow fell, 
or nearly 65 feet; in a record of 38 years the average was 417 inches 
(7). In the period limited by the winters of 1908-09 and 1911-12, 
the average annual snowfall at Tamarack was 515 in., at Emi- 
grant Gap (5221 feet) 249.3 in., and at Glenbrook, Nevada, on the 
east shore of Lake Tahoe, 208.2 in. This last station, elevation 
6282 feet, at the western base of the Carson Range, suggests the 
aridity of that range as compared to the Divide. At Summit on 
May to there is still a mean depth of snow of 20 inches, nor is the 
land fully cleared in average years till May 26. At Tamarack 
the end of June still sees the ground covered every other year. 
Severe frosts may occur at any time throughout the summer, but 
the rubric “killing frosts’? of the weather reports is inapt when 
applied to the high mountains, for the simple reason that the 
plants may be frozen but are not killed. I saw on a morning 
in August plants of Gentiana calycosa stiff and brittle with frost on 
the shoulder of Mt. Tallac, yet in the afternoon the same colony 
was apparently none the worse for the freeze (table D). 
This great burden of snow acts upon the plants of the district 
in at least three ways: it furthers tree growth, but impedes the 
growth of the forest; it favors the meadow, and particularly the 
wet meadow; it favors summer ephemerals. 
In the Tahoe region at present there is no glacial ice, and but 
few snow banks persist for longer than one season. Where these 
occur, they are always on the east or northeast of the ridges and 
peaks, for the prevailing wind from the southwest piles up the 
snow on these exposures. No true snow line exists. 
Alpine winds are keen and drying, and, in spite of their actually 
moving smaller masses of air, exert a marked influence upon the 
forms of plants. ‘Wind cripples” are a constant feature of the 
arboreal vegetation on the higher summits. On Mt. Rose veloci- 
ties of 50 miles an hour have been recorded. In the spring 4 
