4 A Study of the Vegetation of 



Mr. Earle Gibb, my one-time students, the former having assisted 

 me in the field during the entire summer of 1913, and the latter 

 during 1914. Finally, I wish to express my appreciation to Dr. 

 Harry B. Humphrey, now of the Bureau of Plant Industry, and 

 formerly my colleague in the Washington State College, for his 

 kindly interest in the work during the first year of the investiga- 

 tion. 



EXTENT AND POSITION OF THE AREA 



The area under consideration includes approximately 4,000 

 square miles of territory located in southeastern Washington and 

 adjacent Idaho. On the south it extends toward the foothills 

 of the Blue Mountains, and reaches northward to the vicinity of 

 Spokane. Its western limit is about 50 miles from the Idaho 

 boundary, while in Idaho it includes a strip about 15 miles in 

 breadth. This area lies in the eastern part of the great Colum- 

 bia Plateau and extends eastward into the foothills of the Bitter- 

 root Mountains. The 47th parallel of latitude passes through 

 the center of this region, while it is bounded approximately on the 

 east and west by longitude 117 and 118 respectively. Alti- 

 tudinally, it ascends from about 1,175 feet on its western border 

 to a height of 4,000 feet in the mountains. The lowest point, 

 about 520 feet, is reached in the Snake River Valley, while Cedar 

 Mountain, near the Washington-Idaho line, reaches a height of 

 4,950 feet. While the above boundaries limit in a general way 

 the investigations recorded in this paper, without doubt the vege- 

 tation in adjoining regions is not far different from that here 

 described. 



The peculiar topography, together with the range in altitude, 

 gives this area three clearly defined plant formations, ranging 

 from the desert-scrub formation, through the prairie formation 

 to the Pacific Coast forest formation. A brief statement of the 

 geology and topography of the region will help to make clear the 

 reasons for the present distribution of plant communities. 



PHYSIOGRAPHIC REGIONS AND GEOLOGY 



The part of the state of Washington lying east of the Cascade 

 Mountains is divided naturally into three great physiographic 



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