734 
Journal of Agricultural Research 
Vol. XXVIII, No. 8 
the base of the hills is gentle, as in the Gila Valley, this strip of creosote bush 
may be several miles in width. In Coachella Valley where the slope from the 
hills to the valley floor is very abrupt, the creosote bush may be excluded, as at 
Coral Reef. In addition to the areas mentioned above, the creosote bush 
covers slight rises in the valley floor especially where these higher areas are com¬ 
posed of a light porous soil. Due to the fact that such a large portion of the 
creosote bush areas lies above the highest irrigation canals, these areas are not 
cultivated to the extent that the desert-sage lands are. 
With respect to the other plant associations, the cresote bush association lies 
just above the desert-sage and below the giant cactus and paloverde or Yucca 
and cactus associations. 
BOTANICAL COMPOSITION 
Typical areas of creosote bush (Covillea glutinosa (Engelm.) Rydb.) contain 
practically no other shrubs (figs. 4 and 5). Most of the creosote bush land is 
Fig. 4—A 10-meter quadrat in a typical area in the creosote bush association. C indicates the individual 
plants of creosote bush, Covillea glutinosa (Engelm.) Rydb., the only shrub present. The important 
annuals and small perennials were Plantago ereda Morris, Thelypodium lasiophyUum (Hook. & Am ) 
Greene, Pedocaryapenidllata (Hook. & Am.) A. DC., Eremalche exilis (A. Gray) Greene, Abronia villosa 
S. Wats., Chaenadis sp., Chylisma cardiophylla (Torr.) Small, Cryptanthe intermedia (A. Gray) Greene 
and Chylisma scapoidea (Nutt.) Small, Mapped March 2,1915, at Indian Wells, Calif. 
divided by washes, the plant growth of which is very different. These washes 
occur very frequently on the higher slopes so that the uniformity of the creosote 
bush areas is interrupted. At the lower edge of the creosote bush areas where 
the slope is gentle these washes are much wider in extent but not so frequent, 
and the creosote bush areas are much more uniform. The plants occurring along 
the washes are merely a part of the association lying just above the creosote bush 
association. These plants are not included in the lists for the creosote bush areas, 
but are listed under the giant cactus and paloverde or Yucca and cactus associa¬ 
tions. 
The perennial species of plants recorded as occurring in the creosote bush areas 
in Coachella and Gila Valleys are given in the following lists: 
