VI 



LIST OF ILLUSTRATIONS. 



Plate 21. 



A. A sandhill community, showing Red- 



fieldia, Petalostemon villosus, Psoralea 

 lanceolata, and Chrysopsis villosa, with 

 a socies of Eriogonum microthecum 

 at the left. 



B. Roots and rhizomes of Calamovilfa 



longifolia. 

 Plate 22. 



A. Andropogon hallii. 



B. Muhlenhergia pungens. 

 Plate 23. 



A. Consocies of Aletes acaulis on the gravel- 



slide, with Krynitzkia virgata in the 

 foreground. 



B. Quadrat on the gravel-slide, showing 



detail of surface. 

 Plate 24. 



A. Aletes acaulis. 



B. Network of fine rootlets of Aletes. 



C. Smilacina stellata. 



D. Thlaspi alpestre. 

 Plate 25. 



A. Half-gravel-slide, showing Elymus trit- 

 icoides and the large bare intervals. 



Plate 25 — continued. 



B. Elymus triticoides. 



C. Rubus deliciosus. 

 Plate 26. 



A. Koderia cristata. 



B. Calamagrostis purpurascens. 



C. Potentilla arguta glandulosa. 

 Plate 27. 



A. Picea engelmanni consociation, showing 



the forest floor. 



B. Quadrat in the same spruce forest, show- 



ing Haplopappus parryi, Fragaria 

 virginiana, Thalictrum fendleri, etc. 

 Plate 28. 



A. Arctostaphylos uva-ursi, showing a por- 



tion of the root system. 



B. Ribes lacustre, seven years old. 

 Plate 29. 



A. Root systems of ecada of Smilacina stel- 



lata; a, gravel-slide; 6, spruce forest. 



B. Bouteloua gracilis from the sandhills. 



C. Abronia fragrans from the plains. 

 Plate 30. 



A. Opulaster opulifolius, twelve years old. 



B. Chrysopsis villosa from the sandhills. 



TEXT-FIGURES. 



PAGE 



1. A meter quadrat in the Bouteloua com- 

 munity dominating a gravelly 

 ridge at Belmont, near Lincoln; B, 

 Bouteloua gracilis; A, Andropogon 

 furcatus; S, Sporobolus longifolius; 

 M, Meriolix serrulata; Am, Amor- 



pha canescens 9 



2. Root system of Liatris punctata 10 



3. Root system of Kuhnia glutinosa .... 10 



4. Graphs showing the average daily 



temperature (heavy line) and 

 humidity (light line) in the 

 prairie during 1916 22 



5. Graphs showing the average daily 



evaporation rates in the prairie 

 during 1916 (heavy line) and 1917 

 (light line) 22 



6. Schematic bisect showing the root and 



stem relations of important 

 prairie plants. This and figures 

 7 and 8 were drawn from photo- 

 graphs and data obtained by the 

 excavation and examination of 

 325 root systems of these 18 

 species: H, Hieracium scouleri; 

 K, Koeleria cristata; B, Balsam- 

 orhiza sagittata; F, Festuca ovina 

 ingrata; G, Geranium viscosis- 

 simum; P, Poa sandbergii; Ho, 

 Hoorebekia racemosa; Po, Poten- 

 tilla blaschkeana 32 



7. Schematic bisect: S, Sieversia ciliata; 

 W, Wyethia amplexicaulis; LI, 

 Lupinus leucophyllus; Lo, Lupi- 

 nus ornatu^; P, Poa sandbergii; 

 E, Leptotoenia muUifida; A, 

 Agropyrum spicatum 34 



PAGE 



8. Schematic bisect: Hu, Heuchera gla- 

 bella; A, Astragalus arrectus; S, 

 Sidalcea oregana; H, Helianthella 

 douglasii; Ag, Agropyrum spica- 



tum 36 



9. Aristida purpurea 47 



10. Artemisia frigida 47 



11. Gutierrezia sarothrce, showing wide 



lateral spread of roots in the 

 surface soil 48 



12. A small part of caudex of Yucca glauca, 



showing number and extent of 

 horizontal roots, many exceeding 

 25 to 30 feet in length 48 



13. Argemone platyceras 54 



14. Lithospermum linear if olium 54 



15. Lygodesmia juncea 56 



16. Aragallus lambertii 56 



17. Petalostemon purpureus 58 



18. Ratibida columnaris 59 



19. Senecio aureus oblanceolatus 60 



20. Underground parts of Asclepias verti- 



cillata pumila 61 



21. Opuntia camanchica, showing vertical 



anchorage roots 62 



22. Top view of surface roots of Opuntia 



camanchica, showing the wide 

 lateral spread 62 



23. Redfieldia flexuosa, showing rhizomes 



and root distribution 69 



24. Eriogonum microthecum 72 



25. Root system of a ten-year-old Arte- 



misia fiUfolia 74 



