RYDBERG: PHYTOGEOGRAPHICAL NOTES 327 
As stated before, the interchange of species between the two 
great divisions of the Rockies has taken place from the northern 
part of the Wasatch Mountains over the Bear River Mountains 
and the Teton Mountains to the Northern Rockies, or vice versa, 
rather than along the continental divide in central Wyoming. 
Among the Montane plants, I have listed 69 northern species, or 
over 3% per cent of the total flora, which are found in the Wasatchs 
but nowhere else in the Southern Rockies, and 23 Southern species, 
or over I per cent, which are found in southern Idaho or in the 
Teton Mountains, and nowhere else in the Northern Rockies. 
A good deal could also be said about the distribution of the 
plants in the Black Hills, a meeting place of plants from the North- 
ern Rockies, the Southern Rockies, the Canadian and Alleghanian 
Zones of the East, and of the flora of the Great Plains, and I hope 
to take up this subject at some future time. 
NEW YorRK BOTANICAL GARDEN 
