420 Martin: Effect of concentrated solutions 



(i) Cells which had been in 2///3 glycerine for six hours were 

 replasmolyzed by 1.6;/ potassium nitrate. A few were 

 replasmolyzed by 1.5;/ potassium nitrate. 



(2) Those which had been in nJ2 glycerine for six hours were 

 replasmolyzed by 1.5// potassium nitrate; but the concen- 

 tration increased later, so that \.6n was required to pro- 

 duce plasmolysis. 



The concentration did not exceed this in twenty -four hours. 



Urea, (a) Isotonic concentration, — zn{2 urea just plasmolyzed 

 the cells of red beet. 



* ■ 



(^) Increase in concentration of cell-sap, — Sections which had 

 been In 3;//2 urea for seven hours, were replasmolyzed by 1.6// 



urea. 



Acctamid. — 3/2/2 acetamid plasmolyzed these cells in about 

 a minute. The action was a little stronger than with 3?^/2 urea. 

 Turgidity was usually restored in three to ten minutes. 

 (i) 3///2 potassium nitrate plasmolyzed these cells, slowly. 

 (2) 2n potassium nitrate produced too strong a plasmolysis. 



r 



■ (3) n potassium nitrate did not plasmolyze the cells at all. 



Spirogyra 



Fresh Spirogyra was obtained in April, and experiments 

 carried on with this. A few threads were mounted on a 

 slide, under cover-glass, in the plasmolyzing solution, which was 

 drawn off two or three times by filter-paper, and fresh solutions 

 applied. In testing for increase of concentration with glycerine, 

 urea, and acetamid, some Spirogyra was put in the required solu- 

 tions in small vials of about 15 c.c. capacity. In this way plenty 

 oi material could be used, and there was a better opportunity for 

 obtaining uninjured threads. 



Potassium nitrate. Isotonic concentration. — ;//5 potassium 

 nitrate usually produced slight plasmolysis, sometimes a stronger 

 plasmolysis. In some cases, however, there was no plasmolysis 

 produced by this concentration. 



.5 potassium nitrate produced plasmolysis in all cells. 

 The degree varied from slight to rather strong, usually slight. 



In these experiments, as in the others, there were usually one 

 or two threads which were more difficult to plasmohv-e than the 

 others. 



