36 



Snake River in southeastern and southern Idaho, to the westward in the 

 Columbian plain in Washington, and in the northern part of Idaho, where 

 the Clark's Fork of the Columbia cuts its way westward through the 

 mountains, but this great central labyrinth is as yet an unknown land to 

 the botanist, nor is he behind his brother zoologist in this matter. 



With the purpose of beginning a systematic survey that should finally 

 include this whole region, Messrs. J. H. Sandberg, A. A. Heller and my- 

 self, acting under the direction of the Botanical Division of the Depart- 

 ment of Agriculture, undertook at the beginning of the last season the ex- 

 ploration of a portion of this territory along the western border of the 

 mountain ranges. 



In accordance with this plan, we took the field with a camp outfitted at 

 Lewiston, at the head of navigation of Snake river, in the latter part of 

 April, and worked southward till we struck the Craig Mountains, then 

 swinging around northward, followed the line where the foot hills run 

 down to meet the plain, across the basins of the Clearwater and Palouse 

 rivers, Lake Coeur d' Alene, and Clark's Fork of the Columbia river at its 

 expension into Lake Pend d'Oreille. 



This route was chosen because it offered easy access to widely differing 

 areas. To the westward lay the basaltic Columbian plains, with an ele- 

 vation of 700 to 2,500 feet, with its vegetation made up of plants peculiar 

 to the Pacific coast flora; to the eastward, rising in successive tiers, were 

 the secondary ranges, composed of trachyte, limestone, quartz and granite, 

 reaching an elevation of 7,000 feet, with its wide range of plants comprised 

 in the R >cky Mountain flora. 



The difference between these two areas is still further heightened by 

 the peculiarities of the climate. The basaltic plain, during the rainy sea- 

 son, which ends in the latter part of May, supports a dense growth of suc- 

 culent, broad leaved, rapid growing plants, which mature very early. 

 With the close of the rainy season, the soil dries into dust in a very few 

 days, the earlier growth dies, and is replaced by hardy, coarse, narrow- 

 leaved forms which are capable of enduring the extreme heats of the 

 summer. In the mountains, however, the water supply coming from 

 melting snows and springs is more equable, and we have a greater num- 

 ber of plants which endure throughout the season. 



The flora of both regions is characterized by extreme localization. The 

 limits within which a large percentage of the species were collected often 

 comprised no more than a few square yards or a few acres. As examples 



