WHAT WATER DOES IN SOILS 35 



crops. The native plants can do without irrigation 

 because they for the most part either grow during or 

 shortly after the rainy season. Some of them have 

 their roots so deep in the soil as to find moisture where 

 the drought and heat never reach. We should try to 



FIG. 15. Irrigation ditch. The water comes from the mountains which 

 are seen in background. 



make our cultivated plants do the same as far as pos- 

 sible, to save irrigation water and provide against its 

 possible scarcity. 



What are deserts? It used to be said that deserts 

 are lands where nothing useful grows or can be grown. 

 On old maps of the United States we see a large region 



