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 Eriogonum wrightii 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 : 



Bacchans pteronoidcs. 

 Baccharis thesioides. 

 Bouteloua hirsuta. 

 Bouteloua rolhrockii. 

 Castilleja integra. 

 Cordylanthus ivrightii. 

 Crotalaria lupulina. 

 Dalea albiflora. 

 Dalea wislizeni. 

 Eriocarpum gracile. 



Eriogonum pharnaceoides. 

 Euphorbia heterophylla. 

 Gilia multiflora. 

 Gnaphalium wrightii. 

 Hymenothrix wrightii. 

 Linutn neomexicanum. 

 Muhlenbergia gracillima. 

 Pappophorum wrightii. 

 Pentslemon palmeri. 

 Phascolus wrightii. 



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 10s), and also Juglans major, 

 Platanus wrightii, and Populus sp., not to mention the restricted occur- 

 rence of Cupressus arizonica. Shrubs occasionally found along the 



