208 INJURY, EECOVERY, AND DEATH 



In the third method employed by Brooks, 14 strips of 

 the peduncle of the dandelion were placed in hypertonic 

 solutions and the rate of penetration of the salt into the 

 protoplasm was calculated from the rate at which the 



50 



10 



FIG. 91. The ordinates denote the amount of exosmosis into distilled water from living 

 tissue of Taraxacum officinale which had been previously treated with various solutions and 

 then placed in distilled water. Treatment with NaCl produces more exosmosis than treat- 

 ment with a balanced solution, while treatment with CaCh produces less exosmosis. The 

 experiments indicate that the measured exosmosis is largely due to salts present in the cells 

 before the application of reagents. If it were caused by the reagents (by diffusion out of the 

 cell walls and intercellular spaces) it would be greater in CaCh than in NaCl. 



strips recovered their normal shape after being curved 

 by the action of hypertonic solution (the strips remaining 

 in the solution during recovery). This gives the same 

 kind of information as plasmolysis, but avoids the most 

 serious errors of that method. 



In Fig. 92, the rate of recovery is plotted against time. 

 The more rapid rate of recovery in NaCl, KN0 3 , and 

 NH 4 C1 shows that in these salts penetration is more 

 rapid than in the balanced solution. On the other hand, 



14 



Cf. Brooks, S. C. (1910, B). 



