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 i 
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 
4 
