70 ee Study of the Vegetation of 
Crataegus columbiana 2 Ribes cereum 1 
Opulaster pauciflorus 2 Ribes cognatum 2 
Philadelphus lewis 1 Rosa nutkana 1 
Prunus demissa 1 Rosa pisocarpa 2 
Rhus glabra 2 Sambucus glauca 2 
Rhus toxicodendron 2 Spiraea corymbosa 2 
Ribes aureum 2 Symphoricarpos -racemosus 1 
In springy places among the rocks, which are often surrounded 
by thickets, the following herbs are especially plentiful : 
Alsine media Hydrophyllum capitatum 
Cerastium vulgatum Mentha canadensis borealis 
Claytonia parviflora ~ Mimulus langsdorfu 
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 heterophylla 
Arabis holboellu Sisymbrium altissimum 
Crepis gracilis Thalesia uniflora 
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 
7O 
