124 



Water 



Tall grass 

 Short grass 



Mesquite 



I I Desert 



Hjlj Forest 



KM^ Arid Woodland 



Modified from the Graphic Summary of American Agriculture, U. S. Department of Agriculture 



Fig. 4.13. The distribution of the natural vegetation in the United States. 



if we again leave out of account the mountain and coastal regions 

 (Fig. 5.14). Similarly, no good correlation will be found between 

 the occurrence of these principal zones of vegetation and the annual 

 precipitation taken by itself. As already explained, regional dif- 

 ferences in evaporation must also be considered, and water loss in 

 turn depends in part on temperature. Both the supply and the loss 



Desert Plains Prairie Forest 



Fig. 4.14. Schematic representation of the four fundamental vegetational zones 

 in central United States (from This is Our World by Sears, 1937, Univ. of 



Oklahoma Press). 



