May 24 ,1924 Significance of the Southwestern Desert Vegetation 
727 
Associations—Continued. 
Desert-sage- Atriplex polycarpa (Torr.) S. Wats, (desert- 
sage) . 
Seepweed- Dondia torreyana (S. Wats.) Standi, (seep- 
weed). 
Saltgrass- Distichlis spicata (L.) Greene (saltgrass). 
Pickleweed- AUenrolfea occidentalis (S. Wats.) Kuntze 
(pickleweed). 
Minor communities— 
Mesquite and chamiso_ Atriplex canescens (Pursh) Nutt, (chamiso). 
Prosopis glandulosa (Torr.) (mesquite). 
Washington palm- Washingtonia filifera Wendl. (Washington 
palm). 
Arrowweed and saltbush_ Pluchea sericea (Nutt.) Coville (arrowweed)* 
Atriplex lentiformis (Torr.) S. Wats, (salt¬ 
bush) . 
DISTRIBUTION OP THE TYPES OP VEGETATION 
The map (fig. 2) shows the distribution and the respective areas of the vege¬ 
tation types of Coachella Valley. If the types of vegetation of the valley are 
divided into two groups, one including the types above and the other those below 
sealevel, the first group would include (a) Yucca and cactus; (b) creosote bush; (c) 
creosote bush and bur-sage; (d) mesquite and chamiso; and (e) Washingtonia 
palm, as the types above sealevel. The second group: ( f ) desert-sage; (</) arrow- 
weed and saltbush; ( h ) seepweed; (i) saltgrass; and ( j ) pickleweed, the types 
below sealevel. 
The Yucca and cactus area is the type of vegetation highest above sealevel. It 
covers the lower hills on the west side of the valley and broadens out above 
Whitewater over the more level but high lands. 
Bordering on the lower margin is the area dominated by creosote bush. In 
places bur-sage is so mixed with creosote bush that it is of equal importance. 
The lands covered by this type are the fans at the mouths of canyons and the 
higher bench lands skirting the hills on each side and a broad level area across 
the valley between Whitewater and Palm Springs. 
The mesquite and chamiso area embraces the sand dunes and sandy areas. 
These sandy areas occur west and southwest of Indio and also northwest beyond 
Indian Wells, and are the result of the winds blowing down San Gorgonio Pass. 
These winds pick up material in blowing over the higher desert lands, become 
laden with sand and dust and drop their burden wdierever the force of the wind 
is slackened. 
The change of the slope from the fans covered by the creosote bush to the 
adjoining valley floor, covered by the desert-sage, is very abrupt and sets off the 
two associations very definitely, as regards soil texture, soil moisture, and salt 
content. 
While most of the lands covered by the desert-sage are below the sealevel line, 
some are slightly above it. They form an almost continuous belt along the 
sides of and at Indio, across the valley except where the sandhills or the culti¬ 
vated areas break in on them. 
Just below the desert-sage belt, and considerably below sealevel, are the 
narrow irregular strips of saline land covered with Dondia (seepweed). Occupy¬ 
ing the center of the valley is the land covered with arrowweed, saltbush, or 
pickleweed. This is the heaviest, wettest, and most saline type of land in the 
valley. Small meadows formed by saltgrass are scattered within the last two 
types. 
