LIST OF ILLUSTRATIONS. 



PLATES. 



PAGE. 



Plate A. Quadrat-bisect in the half- 

 gravel slide, Alpine Laboratory, 

 Colorado 32 



Plate 1. 



A. Short-grass (Bouteloua gracilis) on 



hard land, Colorado Springs, 

 Colorado 10 



B. Wire-grass (Aristida purpurea) on 



short-grass land, Walsenburg, 



Colorado 10 



Plate 2. 



A. Spirostachys occidentalis in salt 



marsh, Bakersfield, California.. 12 



B. Shadscale (Atriplex confertifolia) in- 



dicating saline land, Rock Springs, 



Wyoming 12 



Plate 3. 



A. Lodgepole forest (Pinus contorta) in- 



dicating fire, Long's Peak, Colo- 14 

 rado 



B. Aspen woodland (Populus tremu- 



loides) arising from root-sprouting 



due to fire, Long's Peak 14 



Plate 4. 



A. Protected pasture in Aristida-Boute- 



loua association, Santa Rita 

 Range Reserve, Tucson, Arizona 22 



B. Fenced quadrat in rotation pasture, 



Bouteloua eriopoda consociation, 

 Jornada Range Reserve, Las Cru- 



ces, New Mexico 22 



Plate 5. 



A. Dominant Agropyrum glaucum and 



8ubdominant Tradescantia vir- 

 giniana in mixed prairie, Winner, 

 South Dakota 30 



B. Agropyrum glaucum in roadway, in 



sagebrush, indicating the rela- 

 tion of water-content to com- 

 petition, Red Desert, Wyoming . . 30 

 Plate 6. 



A. Lowland mesquite (Prosopis juli- 



flora) at 2,500 feet in the San 

 Pedro Valley, Arizona 40 



B. Foothill mesquite meeting oak at 



4,500 feet, Patagonia Mountains, 



Arizona 40 



Plate 7. 



A. Phytometer station in grassland at 



6,000 feet, Colorado Springs, 

 Colorado 46 



B. Battery of oats, gravel-slide station, 



Minnehaha, Colorado 46 



C. Battery of oats, brook-bank station, 



Minnehaha, 46 



Plate 8. 



A. Anogra albicaulis as a serai dominant 



_ in a fallow field, Agate, Nebraska 48 



B. Stipa comata as a climax dominant of 



the mixed prairie, Chadron, 



Nebraska 48 



Plate 9. 



A. Pentstemon gracilis as a climax sub- 

 dominant in mixed prairie, Gor- 

 don, Nebraska 50 



Plate 9 — Continued. page. 

 B. Pedicularis crenulata as a serai sub- 

 dominant in a Juncus-Carex 

 swamp, Laramie, Wyoming 50 



Plate 10. 



A. Stages of a hydrosere from floating 



plants to forest, Pike's Peak, 

 Colorado 52 



B. Stages of a burn subsere from the 



pioneer annuals to the chaparral 

 climax, San Luis Rey, California 52 

 Plate 11. 



A. Normal Campanula rotundifolia at 



8,300 feet, and alpine ecad at 



14, 100 feet, Pike's Peak, Colorado 68 



B. Shade ecad and normal Gentiana 



amarella at 8,300 feet and alpine 

 ecad at 13,000 feet, Pike's Peak. 68 



C. Alpine ecad, normal form and shade 



ecad of Androsace septentrionalis, 



Pike's Peak 68 



Plate 12. 



A. Alternation of sagebrush on southerly 



slopes and Douglas fir on north- 

 erly ones, King's Ranch, Colo- 

 rado 74 



B. Layers of Impatiens, Helianthus and 



Acalypha in oak-hickory forest, 



Weeping Water, Nebraska 74 



Plate 13. 



A. Typha alternes indicating pools in a 



salt-marsh, Goshen, California. 78 



B. Juniperus indicating seepage lines in 



hills of Mancos shale, Cedar, 



Colorado 78 



Plate 14. 



A. Fragaria and Thalictrum, indicators 



of medium shade in montane for- 

 est, Minnehaha, Colorado 80 



B. Mertensia sibirica, indicator of deep 



shade in montane forest, Long's 



Peak, Colorado 80 



Plate 15. 



A. Hordeum plain and Dondia hum- 



mocks indicating differences in 

 salt-content, Great Salt Lake, 

 Utah 84 



B. Communities of Phleum-Equisetum 



and of Juncus-Heleocharis mark- 

 ing differences in water-content 

 and aeration, Sapinero, Colorado . 84 

 Plate 16. 



A. Andropogon hallii indicating stable 



sandy soil in sandhills, Agate, 

 Nebraska 88 



B. Alternes of sagebrush and aspen- 



Douglas fir forest indicating 

 various slope-exposures, King's 



Ranch, Colorado 88 



Plate 17. 



A. Alpine fir (Abies lasiocarpa) at timber 



line, showing the dwarfing effect 

 of high altitudes, Long's Peak, 

 Colorado 90 



B. An alpine dwarf, Rydbergia grandi- 



flora, Pike's Peak, Colorado 90 



XI 



