130 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



be due to oppositely charged ions has been carefully con- 

 sidered by Loeb (1914), and much evidence has been 

 adduced by him against this view. Some years previously 

 Loeb (1899) drew attention to the fact that the action 

 of the ions Na% K*, and Ca" , with regard to the absorption 

 of water by soaps and by muscular tissue, was very similar. 

 Hansteen Cranner (1914) showed that the same parallel 

 held good for their influence upon the absorption of water 

 by roots and by isolated plant cells. These facts lend sup- 

 port to Robertson's (1910) view that the action of calcium 

 in antagonizing sodium is due to its forming insoluble 

 calcium soaps with the plasmatic surface, whereas those 

 of sodium are soluble. 



The effect of acid upon permeability has also been 

 investigated by Osterhout (1914, 5), who found that, while 

 alkali merely increases permeability, an acid, such as 

 hydrochloric, produces a rapid decrease, followed at once 

 by a rapid increase which continues until the death-point 

 is reached. It had been pointed out by Loeb that the 

 effect of acid upon the imbibitional swelling of muscular 

 tissue and upon the duration of the lif e of Fundulus could be 

 antagonized by sodium chloride. Osterhout, too (1914, 6), 

 working as before with Laminar ia, proved by means of 

 conductivity measurements that acid could antagonize 

 the action of sodium chloride, though the degree of antagon- 

 ism was not as great as between this salt and calcium 

 chloride. He further showed that life cannot be main- 

 tained as long in the most favourable mixture of acid and 

 sodium chloride as in that composed of the latter and 

 calcium chloride. These results are considered by Oster- 

 hout as affording additional evidence for the view that 

 the plasmatic membrane of plants is protein in character. 



In addition Osterhout (1915, 1) has shown that the 

 permeability of protoplasm may be greatly increased or 



