RYDBERG: PHYTOGEOGRAPHICAL NOTES 297 
Wind River Ranges. This region may be regarded as a distinct 
subdivision (District 5). 
Numerous species belonging to the Cascade Mountains have 
invaded the Selkirk Mountains in British Columbia and the Bitter- 
root Mountains between Idaho and Montana, and the flora here 
has become more or less Pacific in its character. This region 
(District 3) includes also more or less the western slopes of the 
main range in British Columbia and northern Montana. 
The mountains of Central Idaho, such as the Sawtooth, Sal- 
mon River, and other ranges (District 6) are characterized in the 
Montane Zone rather by the lack of many species found in the 
main range than by the introduction of any considerable new 
element. In the Submontane Zone, however, the character of 
the flora apparently is more like that of the mountains of the 
Great Basin than that of the main range, although the flora of 
this region is not so well known as might be desired. 
The isolated mountains of central Montana, such as the Belt 
Mountains, the Snowy Mountains, the Crazy Mountains, and the 
Little Rocky Mountains, together with the Cypress Hills in 
Canada (District 4), being rather low, are characterized by a 
meagre Montane flora without any additional element. This 
can also be said of the Big Horn Mountains of Wyoming (District 
7), although these are much higher and contain a few strictly 
endemic species. 
The Black Hills of South Dakota and Wyoming are also to 
be counted as a subdivision of the Northern Rockies (District 8), 
although they contain quite a number of species belonging to the 
Southern Rockies as well as many belonging to the Canadian and 
Alleghanian Zones. 
In the Southern Rockies the main range (District 9) includes 
all of the mountains in Colorado and northern New Mexico, 
together with the Sierra Madre, Medicine Bow, and Laramie 
Ranges in Wyoming. Only a few peaks of the latter reach the 
Montane Zone. © 
The Uintah and the northern part of the Wasatch Mountains 
in Utah (District 10), although geologically belonging to the 
Northern Rockies, have a flora closely resembling that of the 
Southern Rockies. In the Wasatch Mountains, however, there 
