362 BOTANICAL GAZETTE [NOVEMBER 
habitat and its lichen assemblage is very much smaller. Caloplaca elegans and 
Parmelia sulcata are frequent on scattered rocks and tree trunks in shaded 
canyon-bottoms. 
oist surfaces in humid recesses of the rocks show numerous lichen species, 
mostly foliose, including Physcia aipolia (Ach.) Nyl. and a number of species 
of Parmelia. osses grow with the lichens abundantly in these situations. 
These distinctly humid recesses are scattered and infrequent in the foothill 
region. A Cladonia, probably C. fimbriata (L.) Fr., is characteristic on moist 
north-facing canyon slopes, amongst mesophytic herbs, or beside surface rocks. 
A pulvinate, finely divided whitish fruticose lichen, Stereocaulon albicans Th. 
Fr., has the growth-form of a pulvinate moss, being “rooted” in moist rock 
crevices, although the aerial part is more or less exposed. It is infrequent. 
SUMAC ASSOCIATION 
Rossins (16, p. 46), distribution on Long Mesa near Boulder. 
As indicated in the synopsis of associations, the shrubs of sumac (Rhus 
cismontana Greene, which is so like R. glabra of the eastern states as to be 
considered identical with it by some botanists) often form a new plant assem- 
blage in denuded xerophytic situations. These are extremely variable, includ- 
ing old roadways, rock talus below road embankments, quarries, or prospect 
holes, stony hillsides where erosion or landslipping has removed much of the 
plant cover, or places which have been burned. In the lower foothills, and at 
the mountain-front, the sumac appears to be quite common after fires, the 
slopes being too dry to allow the establishment of aspens, in most places. The 
shrubs are usually separated, the sparse plant cover of the interspaces often 
being composed of plants of the primitive grassland association. As developed 
in the foothills, the assemblage shows no essential difference from the sumac 
growths of many parts of the United States. In autumn the bright red coloring 
of the leaves makes the community very conspicuous, so much so as to give an 
exaggerated notion of its frequence of distribution. 
FOOTHILLS PRIMITIVE GRASSLAND ASSOCIATION 
CLEMENTS (1, pp. 9-12), gravel slide formation, half gravel slide formation, 
in part; RAMALEY (12, pp. 124-128), Cercocarpus scrub, upland dry grass, and 
foothill sagebrush-grass formations, in part; ScrovEer (21), gravel slide and 
half gravel slide formations, in part. 
The principal herbaceous growth of dry coarse-soil situations in 
the foothills presents very great variability, and is very generally 
distributed, occupying not only large areas by itself, oa oceutring 
in mixture with shrubs and trees tion 
It is perhaps not too much to say that oe a small proportion of 
