284 BOTANICAL GAZETTE [APRIL 
are unwooded at their summits because of wind conditions; their 
sides are compassed by heaps of talus more or less fragmented, but 
not affording a footing for the seedling pine or fir, while below these 
rubble heaps marsh conditions prevail due to the seepage of water 
from the slopes, and the trees are kept at a distance. All of these 
factors, either singly or combined, operate to make the line a very 
sinuous one that divides the true alpine region from the Hudsonian 
forest. 
In that forest the principal trees are the white bark pine (P. 
albicaulis), the silver pine (P. monticola), the Sierra juniper, and 
the alpine hemlock (Tsuga mertensiana). The first is the tree line 
tree of the Sierras par excellence, being found along the whole 
Sierran crest. In the Tahoe region the largest forest of this pine 
is on the southwest flank of Mt. Tallac; here it forms a nearly pure 
stand and decreases from a tree 40-50 feet in height to prostrate 
wind cripples at the base of the actual peak. The finest examples 
of single trees noted grew on’the plateau between Angora Peak and 
Ralston’s Peak. Pinus monticola is not common in the south end 
of the Tahoe district, but increases northward about Cisco. The 
Sierra juniper (J. occidentalis) appears to have an interesting dis- 
tribution about Tahoe; in the Canadian it is always found on the 
slate outcrops, but in the Hudsonian seems to be the chief krumm- 
holz tree of granite basins. It was not noted on the higher lying 
volcanics (andesites). The chief groves of the alpine hemlocks in 
the region are on the Lucile Ridge and in Desolation Valley, where 
along the east side of the valley it forms a pretty continuous forest 
for several miles. Unlike the forest of white bark and silver pines, 
the hemlock forest is dark and the ground flora sparse. In the 
more open pine forest the ground cover is made up in part of Poly- 
gonum Davisiae, Fragaria virginiana platypetala forma sibbaldifolia 
Hall, Lupinus Lobbii, L. meionanthus, L. montigenus, Epilobium 
obcordatum (the last on the higher ridges), Hieracium gracile de- 
tonsum, and Whitneya dealbata. About the edges of the hemlock 
forest were growing Aster Andersoni and Artemisia norvegica. 
Above the forest, rising toward the peaks and arétes, are exten- 
sive talus slopes, and higher still the country rock offers on ledges 
and in crevices lodgement to many plants of peculiar habit and ex- 
traordinary adaptation to their inhospitable surroundings. It is 
