350 Rydberg: Phytogeographical notes 



and the Bear River Mountains of Idaho) and of the higher moun- 

 tains of the Great Basin extending to the eastern slopes of the Sierra 

 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 ar.istata, 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 



^Erigeron Kingii Kentrophyta tegetaria 



\Draha pectinata Macronema discoidea 



Ivesia utahensis Senecio seridophyllus 



Drymocallis pumila 



3. Species common to the Northern Rockies and the Cascade 



Mountains 



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. ' 



