352 WATER MAKES A GARDEN OF THE DESERT 



has small leaves through whose surface little water evaporates. 

 Some plants lack leaves but have instead stiff" hard thorns through 

 which water cannot easily escape; other plants have leathery 



leaves, which are almost 

 impervious to water and 

 hold it safe in spite of 

 hot, dry winds. In the 

 desert only those plants 

 grow which are able to 

 meet desert conditions 

 by having special means 

 of securing water, of 

 storing water, and of 

 preventing its escape 

 through evaporation. 



The cause of scant 

 rainfall. In the East, 

 winds saturated with 

 moisture blow in from 

 the Atlantic Ocean and 

 move westward over 

 low-lying lands. As the 

 winds travel onward 

 their water vapor grad- 

 ually condenses and falls 

 on the land as life-giv- 

 ing rains ; seeds sprout, 

 vegetables thrive, fruits 

 ripen, and forest trees 



grow in strength and beauty. In the West, moisture-bearing 

 winds blow in from the Pacific Ocean, but they soon meet 

 a mountain range (Fig. 220), which robs them of much of 

 their moisture because as winds rise to pass over mountains 



FIG. 218. Yucca, with stiff narrow leaves through 

 whose surface little water escapes. 



