62 NATIVE VEGETATION AS AN INDICATOR 



passed when only a few scattered or stunted plants are 

 found. Generally when such scattered alkali-indicating 

 individuals are found the soil contains some alkali, but the 

 quantity is not clearly indicated. It is only when the 

 plants produce a vigorous growth and occupy the land to 

 the exclusion of non-resistant if not all other species of 

 plants that they may be taken to indicate the kind and 

 quantity of alkali characteristic of their species. 



FIG. 9. ALKALI LAND WHICH is INDICATED BY THE GROWTH 

 OF SHADSCALE. 



It should be kept in mind also that under certain condi- 

 tions alkali-indicating plants may grow well where alkali 

 may not be present in quantities injurious to general 

 crops and that non-resistant plants may be growing well 

 on land so strongly impregnated with alkali that farming 

 would be practically impossible without reclamation. 

 Such conditions as a shallow hardpan, a dry sandy layer 

 of soil, or other conditions which cause the plants to suffer 

 for want of water, as they do when in the presence of ex- 

 cessive quantities of alkali, may allow the presence of the 

 alkali- resistant plants in abundance to the exclusion of 



