1917] VESTAL—FOOTHILLS VEGETATION . 363 
the area in which the rock pine is of frequent occurrence is occupied 
by actual forest; the usual vegetation of the pine-sprinkled upland 
is open, the ground-cover is made up of associations of herbaceous 
plants or low shrubs; prominent among these is the primitive 
grassland. It enters largely into the ground-cover of other mixed 
associations also, in which trees and shrubs other than rock pine 
are conspicuous. The variability of such an open ground-cover as 
€ primitive grassland is so great that no particular set of plants 
can be said to characterize the whole community, although certain 
features are common to all of its variants or consocies: (1) they 
constitute the first vegetation in new and unfavorable habitats; 
(2) this vegetation is sparse and open; (3) it is made up of an 
assemblage of species typical of coarse soils and rather considerable 
exposure to sun and wind, some more commonly in the plains, others 
in the mountain region (many of these plants are common to 
several of the consocies, though some few are typical only in the 
more extreme developments of particular consocies-habitats, as 
Erigeron compositus in packed granite-gravel); (4) as development 
of vegetation proceeds in the several consocies, with accumulation 
of the plant remains, closing of the plant cover, etc., they resemble 
one another more closely, converging into a less open growth, which 
may be known as the foothills dry grassland association, the next 
higher in the genetic series. Many of the species of the primitive 
grassland seem not to be particularly xerophytic, as Thlaspi 
coloradense and Gilia aggregata, for these are active during the early 
part of the season, when the moisture supply is ample. Such 
plants are very widely distributed in the foothills and are not 
characteristic of particular habitats nor of the species groupings 
of particular plant communities. 
A partial list of species of the primitive grassland follows: 
SPECIES LIST: PRIMITIVE GRASSLAND 
Selaginella densa (/) Phlox multiflora 
Aristida longiseta (/) Gilia a 
Stipa comata (J) Gilia pinnatifida 
Bouteloua hirsuta (/) Phacelia a heterophylla (ch) 
‘Koeleria cristata (ch) Oreocar 
Sitanion brevifolium (2) Pentstemon humilis 
