Southeastern Washington and Adjacent Idaho. 71 



dwarfed bunches of Agropyron which is better developed on the 

 talus slope below. This gives way in the deeper soils of the 

 depressions or on protected slopes to various lupines, species of 

 Poa, Balsamorhiza, Hieracium, Gaillardia, and other species. The 

 depressions, if alkaline, may be clothed with dense growths of 

 Distichlis spicata, Spartina gracilis, or Poa brachyglossa and these 

 surrounded by a more or less distinct zone of Elymus condensatus. 

 The vegetational differences often occur in areas so local as 

 to be seen at a single glance. Alternating with a talus slope of 

 lichen-covered basaltic blocks and only a few feet away, may be 

 seen other slopes which at a little distance appear well clothed 

 with herbaceous vegetation. Such are the interesting situations 

 offered by the rocky soils of canyons and scab-lands. 



DESERT SCRUB FORMATION 



In the region under investigation the above formation is repre- 

 sented only in the extreme western part. This formation oc- 

 cupies much of the Columbia Basin, extending eastward to an 

 altitude of about 1,200-1,300 feet, and on southerly slopes much 

 higher. Excepting such species as are confined to the moist 

 ground along perennial streams, the great majority of plants are 

 either shrubs or thick-rooted perennial herbs or short-lived 

 annuals. The most conspicuous and ecologically important plant 

 is Artemisia tridentata. Other dominant species are the rabbit 

 brush, Chrysothamnus nauseosus, C. viscidiflorus, the scab-land 

 sage, Artemisia rigidia } the antelope brush, locally known as the 

 black sage, Kunzia tridentata, and, in alkaline situations, the 

 greasewood, Sarcobatus vermicula\tus. 



The life conditions in this region are strikingly more severe 

 than in the region of the high prairies eastward. During the 

 summer of 1914, Mr. James G. Dickson, my .one-time student, 

 made determinations of water content, evaporating power of the 

 air, and soil temperature for a period extending from July 5 to 

 August 15, at Moxee, Washington, in the heart of this formation. 

 He found that the average daily evaporation throughout the 

 period from standard atmometers was 51 c.c., while during several 

 days in August it reached 74 c.c. The soil moisture at 6 and 12 



