126 UNIVERSITY OF COLORADO STUDIES 
ABUNDANT SPECIES 
Various grasses Opuntia polyacantha 
Artemisia spp. Lesquerella montana 
Townsendia grandiflora Lithospermum linearifolium 
Erysimum asperrimum Aragallus albiflorus 
Senecio spp. Eriogonum flavum 
Tetraneuris acaulis Grindelia sp. 
Tetraneuris lanata Frasera speciosa 
Zygadenus falcatus Leucocrinum montanum 
Astragalus succulentus Astragalus drummondit 
Astragalus crassicarpus Phlox bryoides 
Harbouria trachypleura Aragallus multiceps 
Euphorbia robusta Homalobus caespitosus 
Pentstemon Pentstemon unilateralis 
Cactus missouriensis Mertensia brachyloba 
OccASIONAL SPECIES 
Yucca glauca Helianthus petiolaris 
Chenopodium sp. Arenaria hookert 
Anogra sp. Antennaria sp. 
Carduus sp. 
Upland Dry Grass Formation.—This might be described as a part 
of the valley grassland or it could be called a society rather than a forma- 
tion. If the facts of the case are understood it will, however, make little 
difference what name is used. This formation occurs in patches from a 
few square feet to a an acre in extent scattered along the rock ridges 
wherever there is an accumulation of soil. Plants of this formation 
come from the Cercocarpus Scrub Formation, but shrubs and trees are 
absent. Grasses form a large part of the formation. On exposed 
south-facing hills Yucca glauca is often found with the grass. A list 
of species would include most of those found in the scrub formation. 
Valley Grassland Formation.—As previously noted this occupies 
the lateral valleys of the sedimentary rock region and extends a short 
distance up the ridges. It is made up of grasses and various perennial 
herbaceous plants. In many places there is a considerable mixture of 
wormwood or mountain sage and this if abundant gives color to the 
formation when seen at a distance. Probably there are no species 
entirely confined to this formation since these plants make their way 
as stragglers up among the Cercocarpus bushes all along. The plants 
of the valley also get into the foothills and many true foothill plants are 
