316 Univcrsif !J of California Publications in Zoologij [Vol. 16 



Over tlie foothills aud exposed, lower slopes of the Blue Mountains 

 the yellow pine {Pimis ponderosa) forms the dominant forest. This 

 species seems to be able to endure much drier conditions than any of 

 the other conifers. It is limited in vertical range and is not found on 

 the higher parts of the Blue Mountains. As found near Hompeg 

 Palls yellow pine is in uiany places associated with Douglas spruce 

 (Pscudotsuga taxifolia). The trees in this forest usually grow rather 

 far apart. On the exposed slopes there is little underbrush, but the 

 ground is stony or covered by grasses and prairie plants. On some- 

 what sheltered slopes a considerable amount of underbrush may be 

 developed. In this the ninebark {Opulaster pauciflonis) is most 

 abundant and in places on eastern slopes forms a thick covering to 

 the ground. Other shrubs such as service-berry {Amelanckier) , cur- 

 rants (Rubus), spirea (Spirea), willows (Salix), and alders (Alnus) 

 occur also. On the higher slopes the forest is heavier and Douglas 

 spruce tends to become dominant. 



No trapping was done in the yellow-pine habitat and only inci- 

 dental observations were made in this type of forest. The animal in- 

 habitants are surely much more numerous than indicated in the above 

 list. 



BUCKBEUSH HABITAT AND ASSOCIATION (BLUE MOUNTAIN AREA) 

 Exclusive : 



Taxidea taxus negleeta. 



Major : 



Buteo borealis calurus — summer. Zapus princeps oregonus. 



Spizella passerina arizonae — Eutamias amoenus amoenus. 



summer. Lepus bairdii bairdii. 



.Tunco hyemalis shufeldti — summer. Odocoileus hemionus hemionus. 

 Thomomys fuscus fuscus. 



Minor : 



Colaptes eafer collaris — summer. Citellus eolumbianus oolumbianus. 



Peromyscus manieulatus gambelii. Callospermophihis chrysodeirus 



Evotomys gapperi saturatus. chrysodeirus. 



Microtus mordax mordax. 



Eeported : 



A''ulpes macrourus. Lyn.x sp. 



The principal plant of the buekbrush habitat is the l)uckbrush 

 (Ceanothus velutinus). Associated with this are often willows 

 (Salix). alders (Alnus), and a number of other shrubs. Near the tops 

 of the ridges stunted aspens (Populus tremuloides) sometimes appear. 



