May 24,1924 Significance of the Southwestern Desert Vegetation 
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PERENNIAL SPECIES OF CREOSOTE BUSH ASSOCIATION IN COACHELLA VALLEY 
Common or Frequent 
Covillea glutinosa (Engelm.) Rydb. Abronia villosa S. Wats. 
Franseria dumosa A. Gray. Coldenia nuttallii Hook. 
Lotus strigosus (Nutt.) Greene. Geraea eriocephala (A. Gray) Blake. 
Less Frequent or Rare 
Antirrhinum coulterianum Benth. 
Croton californicus Muell. Arg. 
Eriogonum fasciculatum Benth. 
Gilia densifolia Benth. 
Hesperonia retrorsa (Heller) Standi. 
Hoffmanseggia microphylla Torr. 
Isomeris arborea Nutt. 
Krameria grayi Rose & Painter. 
Nicotiana attenuata Torr. 
Oryzopsis hymenoides (Roem. & Schult.) 
Ricker. 
Hilaria rigida (Thurb.) Benth. 
Aplopappus linearifolius interior (Co- 
ville) Jones. 
Aplopappus linearifolius DC. 
Stillingia linearifolia (Torr.) Small. 
Fig. 5.—A 10-meter quadrat in a representative area of the creosote bush association, showing the individual 
plants of Covillea glutinosa (Engelm.) Rydb. indicated by C, the only shrubby species present. For a 
detail of the annual flora see figure 6. Mapped March 29,1915, Chandler, Ariz. 
PERENNIAL SPECIES OF CREOSOTE BUSH ASSOCIATION IN GILA VALLEY 
Common or Frequent 
Covillea glutinosa (Engelm.) Rydb. Astragalus nuttallianus trichocarpus 
Franseria dumosa A. Gray. Torr. & Gray. 
Sphaeralcea sp. 
Less Freuqent or Rare 
Astragalus sp. Triodia pulchella H. B. K. 
Lycium gracilipes A. Gray. Zizyphus lycioides canescens A. Gray. 
Sphaeralcea coulteri A. Gray? 
There are a large number of annuals found in the typical creosote bush areas 
(fig. 6.) 
Of these the desert plantain (Plantago erecta Morris) is the most abundant and 
has the widest distribution. It occurs as the most important annual both in the 
Coachella and Gila Valleys. Annual fescue (Festuca octoflora Walt.) is the next 
