116 keaeney: plant life on saline soils 



. dry, as well as non-saline. Since the Caetaceae, as Cavara^^ 

 and Livingston^ ^ have shown, are also characterized by a low 

 osmotic pressure of the cell sap, while the succulent halophytes 

 develop very high pressures, it is evident that the relation be- 

 tween succulence and salinity is bj^ no means a simple problem. 

 Schimper and other ecologists regarded halophytes as being 

 xerophj'tes, or drought resistant plants, in that their structure 

 is modified so as to reduce transpiration. Later investigators 

 have shown the one-sidedness of this point of view. It origin- 

 ated largely in the mistaken conception that plants of the sea 

 beaches and dunes, many of which have a markedly xerophytic 

 structure, are really halophytes. ^^ It is true that in arid cli- 

 mates many, but by no means all, salt plants exhibit xeroph\'- 

 tic peculiarities, such as reduced leaf surface, sunken stomata, 

 thick cuticle, highly developed palisade tissue, and small inter- 

 cellular spaces. On the other hand, certain xerophytic charac- 

 ters, particularly hairiness and the excretion of -resin and of 

 aromatic volatile oils, are rarely met with in halophytes, even in 

 those that inhabit deserts.-"^ 



In cool, humid regions, some of the most characteristic salt 

 marsh plants exhibit almost no xerophytic peculiarities, having 

 a thin cuticle, stomata level with the epidermis or even slightly 

 raised, and large intercellular spaces. Terras-' in Scotland and 

 Cross^- in New Zealand studied the anatomy of coastal halo- 

 phytes and concluded that some of them have the structure of 

 aquatic plants rather than of desert plants. 



1^ F. Cavara. Risultali di una serie di ricerche crioscopiche sui vegetali. 

 Contrib. Biol. Veg. (Palermo) 4: 41. 1905. 



1* B. E. Livingston. The relation of desert plants to soil moisture and to evap- 

 oration. Carnegie Inst. Publ. 50. 1906. 



^^ T. H. Kearney. Are plants of beaches and dunes true halophytes? Bot. 

 Gaz. 37:424. 1904. 



-" Detailed descriptions of the anatomy of many European halophytic species 

 and an extensive bibliography are given by H. Chermezon {Recherches anatomiques 

 sur les plantes littorales. Ann. Sci. Nat. IX. Bot. 12: 117-313, ^^s. 7-5^. 1910). 



-^ .1. A. Terras. Notes on the salinity of the cell sap of halophytes. Proc. 

 Scottish Micr. Soc. 4: 152. 1906. 



-2 B. D. Cross. Some New Zealand halophytes. Trans. New Zealand Inst. 

 42:545. 1910. 



