42 A Study of the Vegetation of 
The Festuca Consociation 
This consociation occupies the larger part of the area covered 
by the prairie-plains formation. Along the thin soils of the 
canyons the ecotone between this and the Agropyron consociation 
is often very sharp, but westward and southward it shades im- 
perceptibly into the latter. 
The plants that share in the botanical composition of this con- 
sociation in eastern Washington and adjacent Idaho are given 
in the following lists of species which are classified into three 
groups based upon their relative abundance and ecological im- 
portance, 
Composition of the Festuca Consociation 
Dominant Species 
Agropyron spicatum (includ- Festuca ovina ingrata 
ing var. imerme )* Koeleria cristata 
Balsamorhiza sagittata Poa sandbergu 
Principal Species 
Achillea millefolium lanulosa Leptotaenia multifida 
Astragalus arrectus Lupinus ornatus 
Erythronium grandiflorum Potentilla blaschkeana 
Geranium viscosissimum Rosa nutkana 
Helianthella douglasii Sieversia ciliata 
Hoorebekia racemosa Symphoricarpos racemosus 
Hieracium scouleri 
Secondary Species 
Agoseris grandiflora Arnica fulgens 
Agoseris heterophylla Aster fremonti 
Allium acuminatum Aster laevis geyeri 
Alsine nitens Astragalus spaldingu 
Antennaria luzuloides Bromus brizaeformis 
Apocynum pumilum Bromus hordeaceus 
2 The nomenclature in this paper is that of the Flora of Southeastern 
Washington and Adjacent Idaho, by C. V. Piper and R. Kent Beattie, 1914. 
42 
