356 BOTANICAL GAZETTE [NOVEMBER 
Texture of soil in its influence on water relations is probably 
the most important soil factor in the foothills, so far as local distribu- 
tion of plants is concerned. Especially interesting are some of the 
features of mixed soils, in which fragments of greatly different sizes 
are intermingled. Rocks of all sizes may occur on the surface, or 
buried among finer fragments as rock-débris of detrital slopes. 
Where the large fragments are imbedded beneath the surface in 
fine soil, the water content of the latter appears to be increased. 
1,.—General view in foothills, looking westward to snowy range-crest; fore- 
Fic 
ground a eh slope; general vegetation grassland with scattered pines; southwest of 
Boulder, 7200 ft. 
Where the large rocks are exposed at the surface, moisture condi- 
tions appear to be more favorable immediately beside and under 
them, so that comparatively mesophytic plants are seen growing 
in mixture with xerophytes, the former always growing beside or 
from under the surface rocks. This effect will be noticed in the 
lists of species; many plants are found in both xerophytic and 
mesophytic assemblages. 
The more frequently recurring combinations of topographic and 
atmospheric factors which form effectively different local environ- 
ments for plants may be viewed in the synopsis which follows. It 
is intended to apply only to the foothills proper; a number ol 
situations of the mountain-front belt cannot be included herein. 
