May 24 ,1924 Significance of the Southwestern Desert Vegetation 
739 
moisture-holding capacity of the soil but reduces the penetration. There was 
very little available water, in the first foot when the samples were taken in the 
spring (March 15-27), and the amount was less in the second, third, and fourth 
foot than that found in Coachella Valley. The growing season was well advanced 
Fig. 7.—The daily rainfall in Coachella Valley, Calif., during 1914 and 1915 illustrating not only the char¬ 
acter of the rains but the long periods of continuous droughts which occurred during the years when soil 
moisture studies were being made. 
at that time, so that the available water had been considerably reduced. In 
many places the annuals had matured and were beginning to turn yellow and 
dry up. In comparing the available water in the creosote bush land of the two 
localities a difference of at least two weeks in the season of rapid growth must be 
taken into account. The sampling in creosote bush areas in the Coachella Valley 
was done March 2-3, and that in the Gila Valley March 15-27 (Tables VI and 
VII). 
