KEARNEY: PLANT LIFE ON SALINE SOILS 113 



2. Salt marsh, composed mainly of grasses, rushes, and sedges, 

 with various other annua and perennial herbs as a secondary 

 element. Salt marsh vegetation is found chiefly in temperate 

 regions, where it occurs both on the sea-coast and in very wet 

 saline areas of the interior. 



S. Salt scrub, composed of woody species, in large part Cheno- 

 podiaceae, ranging in size from half shrubs to almost tree-like 

 dimensions. This formation is typically developed only where 

 the climate is arid and the soil is not constantly wet. 



4. The .mangroie formation, of small trees belonging to the 

 Rhizophoraceae and a-few other families. This vegetation occu- 

 pies muddy shores within reach of the tides, in and near the 

 tropics. 



Time permits only brief reference to the fascinating problem 

 of the local distribution of halophytes. The vegetation of saline 

 soils, both along the sea-coast and in the interior, often shows 

 beautiful examples of zonation, determined, in large part, by 

 differences in salinity, although the physical properties and the 

 water content of the soil are likewise important factors. 



The correlations betw^een distribution of the plants and salt 

 content of the soils are often so close as to permit of agricultural 

 classification of the land on this basis, as has been demonstrated 

 by Hilgard^ and his colleagues in California and by Briggs, 

 Shantz and the writer^" in the vicinity of Great Salt Lake. The 

 different types of halophytic vegetation w^ere found to indicate 

 with considerable precision the degree of salinity of the soil 

 and hence w^hether the land is suitable for crop production 

 or could be rendered suitable by the usual methods of recla- 

 mation. The indicator plant method is particularly useful 

 in dry areas where there may be no superficial evidence of 

 salinity but where large quantities of salt may be present in the 

 subsoil. 



The importance of halophytes as geological agents deserves 



' E. W. HiLGARD. Soils, pp. 534-549. ^ew York, 1906. 



1" T. H. Kearney, L. J. Briggs, H. L. Shantz, J. W. McLane, and R. L. 

 PiEMEisEL. Indicator significance of vegetation in Tooele Valley, Utah. Journ. 

 Agr. Research 1 : 365-417. 1914. 



