60) 
vegetation of the Carson Lake region is devoid of many plants 
growing in the Salt Lake region, and in addition it contains many 
Salt Lake City and central Montana, but has not yet reached Col- 
orado. Astragalus tetrapterus has traveled from southern Utah 
and adjacent Arizona northwestward as far as Cobre, Nevada. 
Astragalus scopulorum has traveled from central Colorado to 
Thistle, Utah. Many illustrations of the like, both cultivated and 
native plants, might be given to show the effect of harriers. The 
influence of barriers is very much obscured by slight differences 
of climate which have an infinitely greater effect on the plant for- 
mation than the barriers. This is well illustrated in the Columbia 
Basin, whose peculiar flora is due more to an increased humidity 
than to barriers. Another illustration is the difference in cli- 
mate between that portion of the Great Plateau east of the Rocky 
Mountains and that which is west of them, The Colorado climate 
up to the crest of the mountains, is that of the Mississippi valley, 
which is characterized by a slight rain and snow fal! in the winter 
and a relatively excessive rainfull during the growing season. 
The climate of the region west of the Colorado Rocky Mountains 
gion they are only semi-arid. This is noticeable at once by the 
fact that you can divide these two areas into the sodded and sod- 
less regions. There is practically no sod west of the Rocky Moun- 
tains, while east of the Rocky Mountains the whole region is sod- 
ded to the Atlantic Ocean. The plains are characterized by a 
grassy sod in every direction, while the Great Plateau for the most 
part has only little tufts of grass here and there scatterd among 
the sagebrush and similar shrubs which cover the Great Basin. 
This results in a very great difference in many ways. There are 
very many more annuals and bulhous plants in our region; it is a 
region of omnipresent dust and in the hotter portions, of dust and 
sand. There is 1lso an enormous amount of alkali in almost every 
portion of the Great Plateau, which affects the vegetation in the 
valleys particularly. It makes many of the valleys deserts, whose 
centers contain absolutely no vegetation and whose margins con- 
