Martin: Effect of concentrated solutions 427 



The concentration of the plasmolyzing solution influences the 

 increase in the concentration of sap. nJ2 urea increased the con- 

 centration of sap in Spirogyra 2.99 times, whereas nji urea 

 increased it 2.24 times. The greater increase takes place in the 

 stronger concentration of the plasmolyzing solution. 



This paper was submitted by Professor Atkinson to Professor 

 Wilder D. Bancroft of the Chemical Department, who very kindly 

 read it for the purpose of passing on the question of chemistry 

 involved. He has suggested that the increase in concentration is 

 due to the fact that the solutions, glycerine, urea, and acetamid 

 pass through the plasma-membrane into the cell-sap, until the 

 concentration oi the solutes used is equal on both sides of the 

 membrane, without reference to the concentration of other sub- 

 stances in the sap. Thus the total concentration in the sap may 

 be equal to the original concentration q{ tlic sap plus the concen- 

 tration of the glycerine, urea, or acetamid solutions used. Turgor 

 would be restored when enough of the solution had penetrated so 



that the total concentration within the cell equaled the concen- 

 tration in the external medium. If the plant remained in the solu- 

 tion after the turgor was restored, osmotic action might continue 

 until the concentration of the solutes useji would be equal on both 

 sides of the membrane, and the total concentration would be 

 greater than that ol the external solution. 



This hypothesis would explain the cases where the increase in 

 concentration was equal to or less than the concentration of the 

 plasmolyzing solution, as in the experiments with Tradesca?itia 

 and Philotria, and all the experiments with acetamid. The increase 

 in concentration above that of the external solution, amounting in 

 Beta to 6.88 per cent, and in Spirogyra from i. 33-1.48 per cent, 

 in glycerine solution, seems remarkable. In this connection 

 reference may be made to the conclusion of Loeb (Studies in Gen- 

 eral Physiology, page 553) that "the simple osmotic theory of 

 absorption which has been accepted by botanists cannot possibly be 

 correct." This conclusion was based upon experiments with mus- 

 cles, and Fwtdiilus. " The fact that Fiindtdiis can be thrown from 

 sea-water into distilled water without any considerable swelling, 

 or without any visible injurious effects, may find its explanation 

 through the influence that various ions have upon the absorption 

 of liquids." 



