XII 



ILLUSTRATIONS. 



PAGE. 



Plate 18. 



A. Cereus giganteus showing nests of 



gilded flicker (Colaptes chrysoides) 

 Tucson, Arizona 90 



B. Dalea spinosa dying as a result of the 



work of kangaroo-rats (Dipodo- 

 mys deserti), Glamis, California 90 

 Plate 19. 



A. Aspen indicating an early fire, and 



sagebrush alternes, a recent one, 

 Strawberry Canyon, Utah 92 



B. Artemisia frigida indicating an old 



fallow field, Warbonnet Canyon, 



Pine Ridge, Nebraska 92 



Plate 20. 



A. Opuntia comanchica indicating over- 



grazed pastures, Sonora, Texas. 96 



B. Euphorbia marginata marking road- 



ways, Walsenburg, Colorado... 96 

 Plate 21. 



A. Stipa Andropogon association, Lin- 



coln, Nebraska 120 



B. Stipa spartea consociation, Halsey, 



Nebraska 120 



C. Andropogon scoparius consociation, 



Medora, North Dakota 120 



Plate 22. 



A. Koeleria cristata and Andropogon 



scoparius association, Agate, Ne- 

 braska 124 



B. Erigeron ramosus society, Lincoln, 



Nebraska 124 



C. Detail of society of Psoralea tenui- 



folia and Erigeron ramosus, Lin- 

 coln, Nebraska 124 



Plate 23. 



A. Association of Andropogon furcatus, 



nutans, scoparius and Bouteloua 

 racemosa, Peru, Nebraska 132 



B. Society of Silphium laciniatum in 



Andropogon-Agropyrum associa- 

 tion, Salina, Kansas 132 



Plate 24. 



A. Stipa comata consociation, Pine 



Ridge, South Dakota 136 



B. Agropyrum glaucum consociation, 



Winner, South Dakota 136 



C. Detail of association of Stipa comata, 



Sporobolus cryptandrus and Bou- 

 teloua gracilis, Colorado Springs, 



Colorado 136 



Plate 25. 



A. Agropyrum glaucum and Bouteloua 



gracilis association, Vermejo Park, 

 New Mexico 138 



B. Detail of Agropyrum-Bulbilis asso- 



ciation, Winner, South Dakota. . 138 



C. Polygala alba society in Bouteloua 



consociation, Interior, South 



Dakota 138 



Plate 26. 



A. Bouteloua-Bulbilis association, with 



subclimax of Andropogon scopa- 

 rius and Bouteloua racemosa on 

 butte, Stratford, Texas 140 



B. Dense sod of Bulbilis and Bouteloua, 



Goodwell, Oklahoma 140 



page. 

 Plate 26 — Continued. 



C. Open sod of Bouteloua, Dumas, 



Texas 140 



Plate 27. 



A. Muhlenbergia gracillima and Boute- 



loua gracilis, Manitou, Colorado. 142 



B. Detail of Bouteloua gracilis, Ver- 



mejo Park, New Mexico 142 



C. Hilaria jamesii on a saline plain, 



Delta, Colorado 142 



Plate 28. 



A. Bouteloua-Hilaria association, Em- 



pire Valley, Arizona 144 



B. Bouteloua rothrockii and Aristida 



divaricata, Santa Rita Reserve, 

 Tucson, Arizona 144 



C. Bouteloua racemosa consociation. 



Oracle, Arizona 144 



Plate 29. 



A. Bouteloua- Aristida association, 



Sweetwater, Texas 146 



B. Bouteloua gracilis, Scleropogon brevi- 



folius and Hilaria mutica (valley), 

 B. eriopoda, gracilis, racemosa 

 (hills), Van Horn, Texas 146 



C. Bouteloua gracilis, hirsuta, eriopoda, 



and Aristida divaricata, Jornada 

 Reserve, Las Cruces, New Mex- 

 ico 146 



Plate 30. 



A. Agropyrum-Festuca association, 



The Dalles, Oregon 150 



B. Agropyrum consociation, Missoula, 



Montana 150 



C. Agropyrum consociation on "scab" 



land, John Day Valley, Oregon. 150 

 Plate 31. 



A. Stipa setigera consociation in track- 



way, Fresno, California 150 



B. Avena fatua consocies, with relicts of 



Stipa setigera and eminens, Rose 

 Canyon, San Diego, California. . 150 

 Plate 32. 



A. Artemisia tridentata consociation, 



Henefer, Utah 154 



B. Artemisia tridentata consociation, 



Garland, Colorado 154 



C. Artemisia arbuscula consociation, 



Evanston, Wyoming 154 



Plate 33. 



A. Subclimax sagebrush in bad-land val- 



leys, Hat Creek, Nebraska 156 



B. Alternes of Artemisia and Kochia, 



Strevell, Idaho 156 



C. Sarcobatus, Chrysothamnus, Atri- 



plex and Artemisia, Vale, Oregon 156 

 Plate 34. 



A. Atriplex confertifolia consociation, 



Delta, Colorado 158 



B. Atriplex corrugata consociation, 



Thompson, Utah 158 



C. Atriplex lentiformis consociation, 



Salton Sea, California 158 



Plate 35. 



A. Contact of Basin sagebrush with 

 Coastal sagebrush and chaparral, 

 Campo, California 160 



