1923] SEIFRIZ— SALTS 395 



permeability is evident; otherwise exosmosis of the cell contents 

 and a consequent decrease in osmotic value would have resulted. 

 On the other hand, there is no reason to assume that increased 

 osmotic pressure has been due to a decrease in permeability. The 

 permeability might well remain unchanged, and the change in 

 osmotic value be due to the toxic influence of the entering salt. 



While the reaction of protoplasm to the bivalent cation calcium, 

 in these plasmolytic experiments, cannot be interpreted in terms 

 of permeability, it is quite clear that the bivalent cations strontium 

 and barium cause a pronounced increase in permeability of the 

 Elodea protoplast. This fact is in opposition to the statement of 

 Osterhout (6) that "all the bivalent kations" are able to decrease 

 permeability "to a marked degree." This may be true of calcium, 

 but, on the basis of these experiments, is not true of strontium and 

 barium. It is possible that the difference in the results obtained 

 with strontium by Osterhout and the writer is due to the method 

 of experimentation. It is also possible that the difference is due 

 to the kind of material experimented upon. Osterhout worked 

 on marine plants (Laminaria) . My experiments were done with a 

 fresh water plant. The marked difference in salt content of sea 

 water and river water would undoubtedly have a telling effect on 

 the reaction which an aquatic growing in one or the other water 

 would manifest as a result of treatment in salt solutions. Fitting 

 (1), whose data stand in partial support of the writer's results, 

 worked with the land plant Tradescantia (Rhoeo). He found that 

 "salts for which the plasma has shown itself to be permeable, may, 

 in concentrations approaching the critical plasmolytic concentration, 

 diminish if not ultimately practically put an end to the permeability 

 of the plasma membrane, long before the isosmotic value is reached, 

 and whether the cells are plasmolyzed or not." Fitting worked 

 primarily with KN0 3 , but is of the opinion that other monovalent 

 salts behave similarly. 



Regardless of our interpretation of the experimental results in 

 terms of permeability changes, one fact remains clear, that the 

 reaction of protoplasm to the bivalent ion calcium is markedly 

 different from the reaction of the living substance to the bivalent 

 ions strontium and barium. It is quite evident, therefore, that 

 while strontium, barium, and calcium possess certain physico- 



