LIST OF ILLUSTRATIONS. 



VII 



PAGE 



26. Tradescantia virginiana 74 



27. Root system of Petalostemon villosus . . 75 



28. Gilia longiflora 76 



29. Underground parts of Psoralea lanceo- 



lata, showing root tubercles at a 

 depth of eight feet 77 



30. Ipomoea leptophylla, showing a portion 



of the very extensive root system 78 



31. Krynitzkia virgata. The heavy slanting 



line indicates the actual ground- 

 line 81 



32. Paronychia jamesii 82 



33. Surface view of a single root of Paro- 



nychia jamesii at a depth of 2 to 

 2.5 inches 83 



34. Apocynum androscemifolium, showing 



rhizomes and dense network of 

 roots 84 



35. Pachylophus coespitosus 86 



36. Eriogonum flavum 87 



37. Quadrat-bisect showing root relations 



of gravel-slide plants. This was 

 made along the front of quadrat 

 shown in Plate 23, B : P, Paro- 

 nychia jamesii; A, Aletes acaulis; 

 K, Krynitzkia virgata 90 



38. Solidago oreophila, showing wide- 



spreading lateral and deep cen- 

 tral roots 93 



PAGE 



39. Besseya plantaginea, showing the wide- 



spreading root system 94 



40. Root system of Geranium coespitosum. 96 



41. Root system oi Frasera speciosa 97 



42. Pirola chlorantha 100 



43. Thalicirum fendleri 101 



44. Rhizome and roots of Erigeron asper. . 102 



45. Fragaria virginiana 102 



46. Allium cernuum 102 



47. Rhizomes and root system of Aralia 



nudicaulis 103 



48. Senecio cernuus 106 



49. Heuchera parvij'olia 107 



50. Haplopappus parryi 107 



51. Root systems of ecads of Chamoe- 



nerium angusti folium: a, gravel- 

 slide; b, forest Ill 



52. Fragments of the roots of Yucca 



glauca: a, plains form; b, half- 

 gravel-slide form 114 



53. Allionia linearis from the plains 115 



54. Allionia linearis from the sandhills. . . 115 



55. Abronia fragrans from the sandhills. . 116 



56. Chrysopsis villosa, showing various 



stages of development in the 



plains soU 118 ^ 



57. Euphorbia montana from the plains . . . 120 



58. Euphorbia montana from the half- 



gravel-slide 120 



