LIST OF ILLUSTRATIONS. 



24. Underground portion of Anogra 



cinerea 



25. Underground portion of Chrysopsis 



hispida 



26. Root system of Pentstemon ambigu- 



us 



27. Buffalo grass in short-grass-plains 



association 



28. Root system of Andropogon sco- 



parius excavated in the sand- 

 hills 



29. Bisect through the roots of Aristida 



purpurea growing in the sand- 

 hills 



30. Psoralen tenuifiora in short-grass- 



plains association 



31. Andropogon hallii excavated in the 



sandhills 



60 

 62 

 63 

 73 



80 



84 

 86 

 91 



PAGE 



32. Root system of Avena saliva grown 



in moist silt-loam soil 102 



33. Root system of Trilicum azstivum 



grown in moist silt-loam soil . . 104 



34. Root system of Secale cereale grown 



in sandy soil 118 



35. Root system of Medicago saliva, 2.5 



months old 130 



36. Root system of Melilotus alba about 



4 months old 130 



37. Root system of Helianthus annuus 



about 2.5 months old . . .facing 136 



38. Root system of Trifolium pratense 



about 2.5 months old 137 



39. Mature root system of Trifolium 



pratense 137 



