LIST OF ILLUSTRATIONS. 



VII 



PAGE 



26. Tradescantia virginiana 74 



27. Koot system oi Petalostemonvillos us. . 75 



28. Gilia longi flora 76 



29. Underground parts of Psoralea lanceo- 



lata, showing root tubercles at a 

 depth of eight feet 77 



30. Ipomaea 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 androsaemifolium, showing 



rhizomes and dense network of 

 roots 84 



35. Pachylophus caespitosus 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, Aletcs acaulis; 

 K, Krynitzkia virgata 90 



38. Solidago oreophila, showing wide- 



spreading lateral and deep cen- 

 tral roots 93 



PAGE 



Besseya plantaginea, showing the wide- 

 spreading root system 94 



Root system of Geranium caespilosum. 96 



Root system of Frasera speciosa 97 



Pirola chlorantha 100 



Thalictrum fendleri 101 



Rhizome and roots of Erigeron as per . . 102 



Fragaria virginiana 102 



Allium cernuum 102 



Rhizomes and root system of Aralia 



nudicaulis 103 



Senecio cernuus 106 



Heuchera parvifolia 107 



Haplopappu^ parryi 107 



Root systems of ecads of Chamoe- 

 nerium angasti folium: a, gravel- 

 slide; h, forest Ill 



Fragments of the roots of Yucca 

 glauca: a, plains form; b, half- 

 gravel-slide form 114 



Allionia linearis from the plains 115 



Allionia linearis from the sandhills. . . 115 



Abronia fragrans from the sandhills. . 110 

 Chrysopsis villosa, showing various 

 stages of development in the 



plains soil 118 



Euphorbia montana from the plains ... 120 

 Euphorbia montana from the half- 



gravel-slide 120 



