1915] SMILEY—LAKE TAHOE REGION 281 
carpus cryptanthus, Aster integrifolius, A. yosemitanus, Erigeron 
inmornatus, and Senecio lugens. 
The other tree found commonly in the Canadian is the Sierra 
juniper (J. occidentalis Hook), which in the Tahoe region is con- 
fined exclusively, so far as I could determine, to the slate outcrops, 
never appearing on granite in this lowest of the boreal zones. It 
often attains large girth at base (one measured on the Dick’s Peak- 
Suzy Lake trail was 16 feet in circumference), but branches low and 
reaches a height of 20-25 feet. At Camp Agassiz, at the lower 
limit of the Canadian, it is parasitized by Phoradendron juni perinum. 
The Canadian scrub (chaparral) is a constant feature of the 
vegetation on the dry rocky hillsides: Amelanchier alnifolia and 
Cercocarpus ledifolius continue up from the Transition and are 
associated with Amelanchier glabra, Holodiscus microphyllus, 
Ceanothus velutinus, Arctostaphylos patula, A. nevadensis, and 
Grossularia Roezli. On these dry slopes among the shrubs are found 
Silene Douglasii,G yophytum 1 St ae hneria californica, 
Chaenactis Douglasii, and Eupatorium occidentale. On the slopes 
where the weathering has reduced the rock débris to finer particles 
we find at the top sedums deeply rooted in the loose sand (Sedum 
obtusatum and its close ally Gormania Burnhami), and below, where 
the influence of the water content of the slope becomes appreciable, 
bordering thickets of Acer glabrum (Acer Torreyi Greene), Sorbus 
californica, and below these, Prunus emarginata. Spiraea arbuscula 
occurs at the base of such slopes where the water supply is abundant. 
The true rock plants include Quercus vaccinifolia, the only oak 
of the boreal region, which forms dense espaliers over rounded rock 
surfaces, but is more evident as a cover for the roches moutonnées 
in the glaciated Hudsonian valleys. This shrub seems to be re- 
Stricted to the. granite at Lake Tahoe. Nama Lobdbii is a plant of 
Similar habit and covers many granite boulders about Cisco. 
Other tock-plants are Eriogonum Lobii, E. umbellatum, Sedum 
steno petalum (the last forming extensive patches), Lupinus Breweri 
(a typical dry lithophyte), A pocynum androsaemifolium pumilum, 
Pentstemon J affrayanus, P. deustus, and Hieracium horridum. 
The xerophytic ferns Pellaea Breweri and P. Bridgesii are common 
on the trap outcrops, while another rock fern of similar habit, 
Woodsia scopulina, was seen but once. 
