OBSERVATIONS IN THE COLORADO DESERT 79 



prominence was Rhus ovata, large and vigorous, and as subor- 

 dinate shrubs Simmondsia californica, Stenotus linearifolia, Salvia 

 apiana and Eriogonum fasciculatum. Opuntia basilaris var. 

 ramosa and two spinose platopuntias in many places obstructed 

 passage. Among the stones scattered over the surface grew 

 Pellaea ornithopus, Cheilanthes Fendleri and a small Dudleya. 

 Along the main drainage wash, now dry, but doubtless having 

 some percolating underflow, were a few small cottonwoods (Popu- 

 lus Fremonti var. Wislizeni) and sycamores (Platanus racemosus) , 

 and thickets of Baccharis sarothroides. 



Only at this place has the writer found the sycamore on the 

 desert side of the mountains, but a consideration of the plants 

 growing on this slope will show that, with two exceptions, they 

 all are to be found in greater or less abundance on the cismon- 

 tane side. This is in marked contrast to the vegetation of the 

 hill on the opposite side of the valley, which belongs to the exclu- 

 sively desert flora. 



The two exceptions above referred to are Prunus eriogyna and 

 Condalia Parryi* These two species are often companions, and 

 are found in numerous places, at from 500 to 2000 feet altitude, 

 along the flanks of the range bordering the desert, from White- 

 water, at the eastern base of San Gorgonio mountain, at least to 

 the Mexican bolder. The Prunus seldom exceeds 6 feet in height, 

 and is always a shrub. As seen at this place most specimens 

 contained much dead wood, and the general aspect suggested 

 that their struggle for existence was difficult. Condalia, while 

 often shrubby, is properly a tree, reaching a height of 15 feet 

 usually with a single trunk. Both were loaded (April 1) with 

 fruit more than half grown. 



Time did not permit the ascent of the mountain slope beyond 

 1000 feet above the valley floor, but to have continued it would 

 doubtless have revealed instructive and interesting successions. 



VALLECITO 



The road which descends into the desert follows the course of 

 Carrizo creek, a typical desert "wash," whose sand-filled channel 

 carries water only as the ephemeral sequence of a torrential 



