22 fl> o b t e I s i a 



on the plains. The prevailing winds are 

 from the west. They cause a rapid 

 drying up of moisture, for they are warm 

 and dry. The sun shines brightly most 

 of the time. Cloudy days are rare, ex- 

 cept at the time of the spring snows in 

 April or May. 



Deciduous trees will not grow with- 

 out irrigation except in the creek bot- 

 toms and narrow canons. The plains 

 are covered with plants which show 

 special adaptations to meet the peculiar 

 conditions of climate. There are the 

 succulent cactuses, the hairy sage brush 

 and species of Astragalus, the well pro- 

 tected Yuccas. With many plants the 

 growing season is very short ; thus the 

 sand lily (Leucocrinum montanum) ap- 

 pears first above ground the latter part 

 of April. It soon flowers and develops 

 fruit, and by the middle of June the 

 above-ground parts of the plant have 



