66 NATIVE VEGETATION AS AN INDICATOR 



mals eat only the grass part of the plant leaving the trunk- 

 like stems behind. It is a good alkali indicator for the 

 arid Southwest, but is not common north of the 4oth 

 parallel, or about the center of Utah and Nevada. It 

 has been found growing in a soil with an alkali content 

 of 31,190 parts per million in the upper four feet, although 

 it makes its best growth with about 3000 parts per million 





FIG. 10. GREASEWOOD AND SHADSCALE. THESE PLANTS 

 INDICATE ALKALI IN THE SOIL. 



of total salts. Of the separate salts in soil on which the 

 plants were growing vigorously, the following amounts 

 were found: 



Sodium carbonate 1437 parts per million 



Sodium chloride 387 parts per million 



Sodium sulphate 1227 parts per million 



It has been found growing with over 10,000 parts per 

 million of sodium chloride and 20,000 parts per million of 

 sodium sulphate. The range of tolerance is great; hence, 

 scattered individuals should not be taken to indicate ex- 

 cessive quantities of alkali, although when thick and 



