26 VEGETATION OF A DESERT MOUNTAIN RANGE. 
quently found up to elevations of 7,000 to 7,200 feet, and the latter 
reaches its uppermost limit at 7,800 feet (see p. 30). 
The ground cover of low perennial plants, grasses, succulents, and 
herbaceous species which has been mentioned as characterizing the Upper 
Desert is likewise to be found throughout the Lower Encinal, but does 
not form as close a carpet in the latter region as it does in the former (see 
plates 12, 15, and 16). Throughout the year this irregular carpet does 
much to lend character to the landscape, varying but little in its density 
with the alternating seasons of vegetative activity and of drought rest. 
The scattered polsters of Chrysoma laricifolia are green at all seasons, and 
there is no change in the gray-green foliage of Hriogonum wrightit nor 
in the white tomentose leaves of Artemisia ludoviciana. The perennial 
grasses, many of the other perennial herbaceous plants, and all of the 
ephemerals are either in a resting state or dead throughout the arid 
fore-summer and the arid after-summer, but the only change which 
their rest or death registers in the landscape is a change of its color tone 
from a greenish gray to an almost uniform gray and grayish brown. 
All of the low shrubs and root perennials which were mentioned as 
characteristic of the Upper Desert are to be found occasionally or 
commonly in the Lower Encinal, excepting Franseria tenuifolia and 
Ayenia microphylla. The winter and spring ephemerals are extremely 
few at 4,500 to 5,000 feet, but there is much activity of growth and 
much blooming among the root perennials and low shrubs during the 
months of February and March, and sometimes during the early part 
of April. The humid mid-summer is a season of even greater activity 
on the part of the smaller elements of the vegetation. Relatively few of 
the conspicuous herbaceous plants which are active at 5,000 feet in the 
mid-summer have extended upward from thebajada, and the number of 
summer ephemeral species is very small as compared with the Desert. 
Among the small shrubs, root perennials and other herbaceous plants 
which are common during the humid mid-summer at 4,500 to 5,500 
feet, in the Lower Encinal, may be mentioned: 
Baccharis pteronoides. Eriog phar ides. 
Baccharis thesioides. Euphorbia heterophylla. 
Bouteloua hirsuta. Gilia multiflora. 
Bouteloua rothrockii. Gnaphalium wrightii. 
Castilleja integra. Hymenothriz wrightii. 
Cordylanthus wrightit. Linum neomexicanum. 
Crotalaria lupulina. Muhlenbergia gracillima. 
Dalea albiflora. Pappophorum wrightii. 
Datea wislizeni. Pentsiemon palmeri. 
Eriocarpum gracile. Phaseolus wrightit. 
On the flood-plains and along the streamways of the Lower Encinal 
may be found a greater number of individuals of the evergreen oaks 
than on the surrounding slopes (see plate 108), and also Juglans major, 
Platanus wrightii, and Populus sp., not to mention the restricted occur- 
rence of Cupressus arizonica. Shrubs occasionally found along the 
