11 



iug- the observations south to the Colorado- Wyoming line. Here was 

 found the region of the ideal summer pasture, an area which those who 

 depend upon the desert for winter forage utilize for summer range. 



The return to Rock Springs was made by another route, the midway 

 watering place being at "The Gap," a pass through a range of hills. 

 This journey, both going and returning, was made so leisurely as to 

 afford ample opportunity for collecting and observation. This glimpse 

 of the rich summer range to the southwest of the desert made it desir- 

 able that more should be known of the forage which fattens for the 

 autumn markets so much of the stock whose winter range is in the 

 desert. Accordingly, observations and collections, both east and west, 

 were made. For points west, Evanston and Granger were selected, 

 and were visited in late July and again in late August and early Sep- 

 tember. For points east, some localities in the Medicine Bow Moun- 

 tains of Albany County and in the Sierra ]\Iadre Mountains of Carbon 

 County, were chosen for investigation. Outfitting for this latter work 

 at Laramie, the first three weeks of August were devoted to the inves- 

 tigation, resulting in large and interesting collections. 



A knowledge of the forage of the summer range adjacent to the Red 

 Desert is interesting and valuable from the fact that the floras of the 

 two areas are complementary to each other, each rendering the other 

 available by giving range forage througliout the year to the stock of 

 the region. IJecause of clinuitic and vegetal conditions one is unsuita- 

 ble during tliat part of the year when the other is at its best. 



LOCATION AND EXTENT OF THE RED DESERT. 



The area originally designated by the name Red Desert is but a small 

 part of what is now considered as within its boundaries (see PI. I, fig. 1). 

 The name was first applied to a tract, ])ossibly less than 15 by 20 

 miles in extent, characterized by the peculiar red clay soil of the 

 Wasatch Eocene formation. Xear the center of this limited but really 

 red desert area we find the side track and section house on the Union 

 Pacific bearing the designation '' Red Desert." 



The larger Red Desert as now understood includes, however, all that 

 arid section of salt-impregnated soil in southern Wyoming, in which 

 the salt-sages predominate, and which, on account of the absence of 

 suitable stock water, can only be used for winter pasture. The stock 

 owner who speaks of his stock '' feeding" (not " grazing") in the Red 

 Desert uses the name of the region in this comprehensive sense. 



This region includes, when bounded in this way, a well-marked plant 

 formation or area. It may be said to extend from the Platte blufts 

 on the east to the Green River blufts on the west; from the northern 

 limit of Sweetwater County to the hills and mountains separating Colo- 

 rado and Wyoming on the south. Geographically, then, it is situated 

 between latitudes 41° and 42° 20' north and longitudes 107° to 10}>o 

 30' west. Excluding from this rectangle the southwest corner, which 



