May 24,1924 Significance of the Southwestern Desert Vegetation 
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PERENNIAL SPECIES OF THE DESERT-SAGE ASSOCIATION IN GILA VALLEY 
Common or Frequent 
A triplex polycarpa (Torr.) S. Wats. Atriplex canescens (Pursh) Nutt. 
Lyciurn parviflorum A. Gray. Atriplex linearis S. Wats. 
Lyciurn gracilepes A. Gray. Prosopis glandulosa Torr. 
Less Frequent or Rare 
Baccharis sp. Sphaeralcea coulteri A. Gray. 
Isocoma wrightii (A. Gray) Rydb. Sphaeralcea fendleri A. Gray. 
Fig. ll.—A 10-meter quadrat in a typical area of desert-sage, showing the location of each individual 
plant of Atriplex polycarpa (Torr.) S. Wats, indicated by A, and of Atriplex canescens (Pursh) Nutt., 
indicated by Ac, the only woody plants present. A circle around the letter indicates a dead plant. 
The small figures indicate the number of stems to each plant. See figure 12 for a detail of the annuals. 
Mapped March 29,1915, Chandler, Ariz. 
The number of annuals in the desert-sage areas as compared to that of the 
creosote bush or mesquite and chamiso areas is much smaller in both valleys. In 
Coachella Valley where flood waters frequently deposit a thin layer of silt which 
dries to form a crust, annuals often appeared only along the cracks in the silt. 
The number of annuals, both as to individuals and species, increases as the surface 
of the soil becomes lighter and more permeable. In the desert-sage areas Plantago 
erecta Morris is the most important annual in both valleys. In the Gila Valley 
Baeria artistata (Nutt.) Coville is also important (fig. 12). 
The following lists give all the annual and biennial species noted in the desert- 
sage areas. 
