118 KEARNEY: PLANT LIFE ON SALINE SOILS 



Rosenberg'-^ and Delf^^ on salt marsh plants in northern Europe 

 and Von Faber's" investigations of mangroves in the East Indies 

 have shown that many halophytes transpire freely when growing 

 in their normal habitats.-^ 



In conformity with these results as to transpiration, Ganong^^ 

 and HilP° have proven that high osmotic pressures are developed 

 in the roots of halophytes. Difficult absorption of water can- 

 not, therefore, be a universal condition of existence for this 

 type of vegetation. 



The salt plants are evidently able to carry on normally the 

 processes of photosynthesis, metabolism, and growth, notwith- 

 standi*ng the presence of much salt in their cell _ sap This is 

 sufficient proof that they are not inconvenienced by the high 

 osmotic pressures in their cells nor by the specific toxicity of the 

 salt. It is clearly not permissible to draw conclusions as to the 

 normal physiology of halophytes from the pathological condi- 

 tions induced in nonhalophytes by exposure to concentrated 

 salt solutions. 



Our knowledge of the physiology of halophytes is one-sided, 

 since it has been gained chiefly by the study of salt marsh plants 

 in northern Europe and of the mangrove formation in the tropics. 

 Neither of these environments affords such extreme conditions 

 as must be endured by plants inhabiting saline soils in desert 

 regions. Here the atmospheric conditions ' are conducive to 

 excessive transpiration, while enormous fluctuations in the water 

 content of the soil and in the concentration of the soil solution 



2^ O. Rosenberg. Ueber die Transpiration der Halophyten. Kongl. Vetensk. 

 Akad. Forhandl. 53L 1897. 



2^ E. M. Delf. Transpiration and the behavior of stomata in halophytes. 

 Annals of Botany 25: 485. 191L 



2' F. C. VON Faber. Ueber Transpiration und osmotischen Driick bei den 

 Mangroven. Bee. Deutsch. Bot. Ges. 31: 277. 1913. 



2* It has been ascertained by Holtermann and by Ruhland, however, that 

 in halophytes grown in strongly saline soils and having a high concentration of 

 the cell sap, the quantity of water transpired is smaller than when the same 

 species are grown in the absence of an excessive quantitj^ of salt. 



29 Bot. Gaz. 36:358-362. 1903. 



'" T. G. Hill. Observations on the osmotic pressures of the root hairs of certain 

 salt marsh plants. New Phytol. 7: 133. 1908. 



