INJURY AT THE SURFACE OF THE SOIL 



39 



centra tion to cause the modifications of structure noted, 

 transpiration is much reduced. On the other hand, the 

 same salts when present in amounts too small to produce 

 any measurable influence upon structure have a decidedly 

 stimulating effect upon transpiration. 



Fig. 5. The Lower Part of an Orchard being Killed by 

 Alkali brought to the Surface by a Rising Water Table. 



Similar modifications in structure have been pointed 

 out by Kearney (7) who shows that thickness of leaves and 

 stems with zerophytic tendencies characterizes plants 

 growing in a saline soil. 



Injury at the Surface of the Soil. Orchards and vine- 

 yards in many cases have been planted in soils containing 

 a rather high salt content, but not high enough to prevent 

 growth. A root system may become thoroughly estab- 

 lished in an untoxic lower layer of soil which is slightly 



