350 RYDBERG: Puy APHICAL NOTES 
and the Bear River Mountains of Idaho) and of the higher moun- 
tains of the Great Basin extending to the eastern slopes of theSierra 
Nevada. These plants are very few in the Subalpine Zone, more 
in the Montane, and still more in the Submontane and Upper 
Sonoran. Some of these are listed under the endemic element of 
the Rockies, as it is very hard to tell whether their original homes 
are in the Rockies or in the Basin mountains. To this element 
belongs one tree, Pinus aristata, growing on dry southern slopes 
from Colorado west to eastern California. It is perhaps more 
frequently met with in Colorado, but it might have originated on 
the eastern slopes of the Sierra Nevada, as its only close relative, P. 
Balfouriana, is also found there. The following is a partial list 
of the plants of this category: 
Tree 
Pinus aristata 
Herbs 
tErigeron Kingii Kentrophyta tegetaria 
{Draba pectinata Macronema discoidea 
Ivesia utahensis Senecio seridophyllus 
Drymocallis pumila 
3. SPECIES COMMON TO THE NORTHERN ROCKIES AND THE CASCADE 
MOvuNTAINS 
As the Northern Rockies and the Cascades are connected by 
several mountain chains in British Columbia, it is very hard to 
decide where these common plants should be counted, to the 
Rocky Mountain flora or to the flora of the Cascades. It is 
probable that to the former should be counted those which are 
generally distributed in the main chain of the Rockies in Alberta 
and Montana, especially if their range extends south into the 
Yellowstone Park. I would even include in the Rocky Mountain 
flora such species as Larix Lyallii (although very local), which 
crosses the main range at a few places, while I would count Tsuga 
Mertensiana, which extends east only to the Bitter Root and Selkirk 
Mountains, to the Cascade element. 
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