14 



toxic effects of alkali by a decreased rate of transpiration. 



While the alkali condition of the soil which supports 

 saltgrass is sometimes excessive, nevertheless drainage has 

 reclaimed numerous areas which it formerly covered. 



The big greasewood found on subirrigated lands from the 

 Canadian to the Mexican borders is also recognized as an indi- 

 cator of ground water. As with other ground-water plants, the 

 more luxuriant growth occurs where the zone of saturation is 

 within a few feet of the surface, but according to Me Inzer (19) 

 it is, like the mesquite, sometimes able through its large 

 deeply penetrating taproot, to extract moisture from the soil 

 to depths of 40 feet or more. It is an indicator also of alkali 

 in the soil, but under proper systems of irrigation and drainage 

 greasewood areas have good possibilities of becoming agricultural 

 districts. 



Mesquite, saltgrass, and greasewood are but a few of the 

 many ground-water plants common to western regions, and it is 

 neither necessary nor possible to describe all such growth within 

 the limits of this report. Data on the relation of plants to 

 ground water have been listed by Meinzer (19) as a basis for fur- 

 ther investigation, realizing, however, that such generalizations 

 may be questioned. 



Marsh Vegetation 



Chief of this group are plants, the roots of which ordin- 

 arily grow in water or in very wet soil. Typical examples are the 

 cattail ( Typha sp . ) , tule ( Scirpus acutus ) , and sedges ( Carex sp . ) 

 which belong to that group of water-loving plants known as hydro- 

 phytes. These and others of similar habits, through transpiration, 

 dispose of large quantities of water from the surfaces of ponds, 

 lakes, marshes, and running streams, and probably have a greater 

 effect upon the water supply of streams than any other group of 

 plants of equal area. 



Both tules and cattails are common in many regions. Prior 



