20l] FLORA OF COLUMBIA AND VICINITY 59 



scantia. The tall riparian grasses are frequent. Veratrum 

 Woodii, and, locally, Carex Albursina and Allium tricoccum, are 

 conspicuous for their broad leaves. Uniola latifolia is a charac- 

 teristic grass. Aquilegia Canadensis and Cystopteris fragilis are 

 common also. 



3. Rupestres rimosae. The crevice and cranny vege- 

 tation of the naked rocks occupies commonly the upper portions 

 of the cliffs, but occurs wherever nude rocks and ledges are 

 present. The crevices with a deep soil bear a vegetation of a 

 mesophytic type, which is often identical with that of the clivose 

 subzone. Aquilegia Canadensis, and Solidago Drummondii are 

 especially characteristic. The shallow crannies and narrow 

 cracks are occupied by certain xerophytic ferns and a few flow- 

 ering plants. The rimose vegetation attains its best develop- 

 ment upon the cliffs of the Missouri river. A striking feature 

 of these naked cliffs are the lianas that cover their surfaces. 

 Practically all the rimose plants can be gathered into two asso- 

 ciations : 



a. Rimosae quinarioides. The Virginia creeper asso- 

 ciation of cliff lianas commonly mantles the sheer faces of cliffs 

 in the manner of the ivy. These root in cracks and faults of 

 the rock, and cling with their disc-bearing tendrils or aerial 

 rootlets to the steep walls. Quinaria quinquefolia and Rhus 

 Toxicodendron are by far the commonest cliff lianas, though 

 others such as Campsis radicans, Celastrus scandens, and very 

 rarely Lonicera grata, occur also, twining in trees and trailing 

 over the rocks. 



b. Rimosae pellaeoides. The cliff-brake association 

 consists of a few rock ferns and cliff phanerogams. Aquilegia 

 Canadensis, Heuchera hispida, Solidago Drummondii, IVoodsia 

 ohtusa, and Cystopteris fragilis are common in the deeper crev- 



