Plants Used by he e P on Mountain Range. 7 



of the Washington Agricultural Experiment Station by Mr. J. S. Cotton, 

 who, in the years 1901 to 1903, investigated the winter ranges of cen- 

 tral Washington and the summer ranges in the adjacent parts of the 

 Cascade mountains, The dominant plant of the sage-brush region is 

 naturally the sage-brush, Artemisia tridentata Nutt., which is accom- 

 panied by rabbit brush, Chrysothamnus nauseosus (Pall.) Britt., and 

 antelope brush, Kunzia tridentata (Pursh) Spreng., and others. The 

 region is hot and dry in summer and its sparse covering of the more 

 tender herbs and grasses wither or cure into hay as the dry season 

 approaches. 



THE YELLOW PINE FORESTS. 



From the standpoint of plant geography, the yellow pine forests 

 form the upper part of the Arid Transition region (18) (17). If the 

 sage-brush region be taken as a center, the yellow pine region is the 

 second concentric zone lying around it. Between the two lie the bunch- 

 grass prairies of the lower part of the Arid Transition zone. These will 

 be considered later. 



In eastern Washington, the yellow pine forests lie in general be- 

 tween altitudes of 1800 and 3300 feet (18, page 50), but in the 

 eastern part of this region in Latah county, Idaho, and especially in the 

 Mica mountains, the region of this investigation, the upward ex- 

 tension of the yellow pine is somewhat greater. The yellow pine as a 

 dominant tree here reaches 4500 feet, although the underbrush changes 

 to that more typical of the white pine region at about 4000 feet. 



The principal species of this forest is the western yellow pine, Pinus 

 ponderosa Dougl. This is an important timber tree which in this region 

 frequently reaches a diameter of three feet and a height of one hundred 

 feet. Here the yellow pine forests cover granitic hills and mountains 

 and are open in character. 



Mixed with the yellow pine is a considerable amount of western 

 larch or tamarack, Larix occidentalis Nutt. On one of the southwesterly 

 ridges of the Mica mountains, in limited localities, it dominates certain 

 parts of the ridge and occur? in almost pure stand. Elsewhere in the 

 region it is scattered or is occasionally abundant on steep slopes. 



Spruce, Picea engelmanni Parry, lodgepole pine, Pinus contorta 

 Dougl., and Douglas fir, Pseudotsuga mucronata Raf., form secondary 

 species in the yellow pine forest. There is very little second growth 

 timber except in clearings where it usually consists of lodgepole pine, 

 Douglas fir and white fir, Abies grandis Lindl. 



A considerable amount of shrubby growth occurs in clumps espe- 

 cially just below the crest of the hills where it sometimes forms dense 

 thickets, but it nowhere presents the uniformly thick undergrowth so 

 characteristic of the white pine forest to be described below. The shrubs 

 of the yellow pine forest consist chiefly of buckbrush, Ceanothus san- 

 gumeus Pursh, nine-bark, Opulaster paudflorus (T. & G.) Heller, 



