120 KEARNEY: PLANT LIFE ON SALINE SOILS 



accommodate their osmotic pressure to fluctuations in that of 

 the medium. Hill found this to be the case in the root hairs of 

 Salicornia. Von Faber observed that the pressure in the leaf 

 cells of mangroves varied with the salinity of the soil solution. 

 Cavara found that in Italian salt marsh plants the pressures 

 were from 2 to 3 times as high after a long dry period as during 

 the rainy season. The enormous power of osmotic accommoda- 

 tion possessed by many bacteria, fungi, and algae is well known. 

 Plants that inhabit the waters and shores of estuaries and 

 tidal creeks, where daily fluctuations of great magnitude in the 

 salinity of the medium occur, must possess the ability to alter 

 their osmotic pressure rapidly. ^^ 



SALT CONTENT OF THE TISSUES 



Various means are employed in developing these high pres- 

 sures. In some cases the salt absorbed from the soil solution 

 appears to be the principal factor, while in other cases organic 

 compounds elaborated by the plant itself (carbohydrates, tan- 

 nins) play the chief part. Fitting found that among species 

 growing side by side in the Sahara Desert, and manifesting ap- 

 proximately the same resistance to plasmolysis, some had a 

 highly saline cell sap, while in others there was no noteworthy ac- 

 cumulation of salt. He concluded that the maximum amount 

 of salt that can be accumulated in the tissues is a character 

 of the species, independent, in large measure, of transpiration 

 and of the salt content of the soil. 



Many halophytes take up sodium and chlorine in greater 

 proportion than these occur in the soil solution. Such plants, 

 even when grown on soils containing only traces of these ele- 

 ments, may accumulate large quantities in their tissues. ^^ 



Schimper^^ ascertained that certain weeds that are character- 



'* An interesting example of such accommodation is described by W. J. V. 

 OsTERHOUT {The resistance of certain marine algae to changes in osmotic pres- 

 sure. Univ. Calif. Publ. 2: 227. 1906). 



^" G. Paris found that the leaves of a species of Atriplex, when growing on a 

 soil containing the merest trace of chlorides, had an ash content of 37 per cent 

 and a chloride content of 10 per cent of the total dry weight {SuV Atriplex hali- 

 mus L. Staz. Sper. Agrar. Ital. 44: 141. 1911). 



^^ A. F. W. ScHiMPER. Die indo-malayische Strandflora, p. 142. 1891. 



