332 BOTANICAL GAZETTE [November 



+ 



androsaemi folium. A few species from the adjoining plains are invad- 

 ing the formation. These include an occasional Artemisia sp, and 

 a few individuals of Feshica octoflora. Eleocharis palustris wanders 



in occasionally from nearby meadows. 



While the under layer of the formation is so mixed that it is diffi- 

 cult to assign a dominant r61e to any forms, yet in general it may 

 be said that this layer is characterized by Agrostis alba and Melilotus 

 alba. The vernal aspect is not derived from any species or group 

 of species, the color of the vegetation at this season being mainly 

 green. In its late aestival and autumnal aspect the yellow of Solidago 

 and Helianthus gives to the vegetation its predominant color. 



In the lower canons {fig* 5) the formation maintains the loose 

 straggling character which it presents on the plains. Here, however, 



most 



( 1^^^' 5j ^) • Chief among these are Alnus tenui- 

 ita. Other members of this laver are Crataems 



folia and Corylus rostrata. Other 

 cerronisj C coloradoensis^ Clematis ligiisticifolia, A?npelopsis penta- 

 folia, Primus americana^ P. melanocarpa, Rosa pratincola, and Acer 

 glahriim. In the densely shaded thickets formed by these shrubs, 

 the under layer is composed mainly of Hydrophyllum Fendlerij Viola 

 canadensis^ Galium trifidtimy and Vagnera stellata. Species from 

 the higher slopes occasionally wander in, such as Berberis Fendleri 

 and Prunus melanocarpa. 



In places where the light value falls as low as 5 : 300, the under 

 layer is largely lacking. 



Mixed as is this formation on the plains, in the narrow and steep- 

 sloped canons its continuity is still more difficult to follow. The 

 species from the adjoining shrub-grass formation of the canon sides 

 come down to the bottom of the canon and minde with those of the 



o 



cottonwood-willow formation, ruderals are numerous, and along the 



stream banks members 



such as CoU 



paruifloray Mimulus minor, and Veronica peregri 



Whcre\ 



Populus 



invading them in large numbers. Such invasions, for the most part, 

 are only temporary, however, on account of the floods which in spring 

 overflow these sandbars, destroying the plants on them. 



