VOLUME LIX NUMBER 4 
THE 
BOTANICAL (GAZETTE 
APRIL 1915 
THE ALPINE AND SUBALPINE VEGETATION OF THE 
LAKE TAHOE REGION 
Eee SMILEY 
(WITH FOUR FIGURES) 
Geology 
The country rock of the region is mainly a coarse granite, 
which represents the ancient Sierran batholith. The sedimentary 
rocks which formed the more ancient surface, and under which the 
intrusives were thrust, have been for the most part completely 
eroded away; what little remains, as on the summit of Mt. Tallac, 
has been changed by pressure and heat into schistose rocks, and 
these have become deeply fissured by jointing. Under the de- 
grading influence of the alpine climate, with rapid changes of 
temperature and moisture, these jointed slates and schists have 
been ever more deeply fractured and loosened from place, giving 
tise to the immense heaps of angular talus, which skirt the bases 
of Mt. Tallac, Maggie’s Peaks, and Castle Peak. The metamor- 
Phosed sedimentary rocks increase southward, but Rerp (z) points 
out that ‘‘The largest areas are little more than a veneer over the 
granite, so that it is evident that the work of removing the roof of 
the granite is nearly complete.” 
With the granite the course of events has been in part similar, 
in part quite different, depending upon the amount of jointing. 
Where the granite is deeply fissured, the rock is quickly broken to 
fragments of varying size, and these, falling from place, are soon 
reduced to coarse sand, often deeply colored with iron. Where the 
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