70 A Study of the Vegetation of 



Crataegus columbiana 2 Ribes cereum I 



Opulaster pauciflorus 2 Ribes cognatum 2 



Philadelphus lewisii I Rosa nutkana i 



Prunus demissa I Rosa pis o car pa 2 



Rhus glabra 2 Sambucus glauca 2 



Rhus toxicodendron 2 Spiraea corymbosa 2 



Ribes aureum 2 Symphoricarpos racemosus I 



In springy places among the rocks, which are often surrounded 

 by thickets, the following herbs are especially plentiful : 



Alsine media Hydrophyllum capita-turn 



Cerastium vulgatum Mentha canadensis borealis 



Claytonia parviflora Mimulus langsdorfii 



Equisetum arvense Saxifraga columbiana 

 Equisetum hyemale robustum Scutellaria angustifolia 



Galium aparine Vagnera sessilifolia 



Galium asperrimum Veronica americana 



Among the most typical crevice plants other than those previ- 

 ously enumerated may be mentioned two ferns, Cheilanthes gracil- 

 lima and Woodsia oregana. The former is especially character- 

 istic of stony outcrops on the buttes and mountains. Heuchera 

 glabella should also be mentioned here. 



Other species peculiar to thin soils of rocky ledges are: 



Amsinckia intermedia Phacelia he'terophylla 



Arabis holboellii Sisymbrium altissimum 



Crepis gracilis Thalesia unifiora 



Gilia aggregata Valerianella macrocera 



The kaleidoscopic character of scab-land vegetation may well 

 be anticipated by a glance at Fig. 39. 



In the thin soil surrounding lichen- or moss-covered basalt may 

 be found herbaceous plants characteristic of the Poa-Polygonum 

 community. Or these may alternate with the shrubby growth 

 of scab-land sage. In the crevices of the rocks may be seen 



70 



