ON PLASMOLYSIS. 155 



quite independently of them, I had already arrived at conclusions 

 in the main similar to them, as the result of observations on 

 the plasmolysis of the prothalli of ferns, which were instituted 

 with a very different object, viz. that of finding whether plas- 

 molytic contraction of the protoplasmic body would be a good 

 method for preparing the apical region of the prothallus, so as 

 to show the form and arrangement of the individual cells. It 

 was impossible to overlook the fact that strings of protoplasm 

 are very universally to be seen connecting the contracted 

 protoplasm with the cell wall in cells of prothalli thus 

 prepared. 



For the reasons which determined the choice of De Vries 

 (1. c, pp. 7 — 13) I have adopted as the dehydrating agent solutions 

 of common salt of varying strength, from 1 per cent, to 10 per 

 cent., according to the requirements of the object under treat- 

 ment. It has been my practice to use as weak a solution as 

 will suffice to bring about the desired result, and it will be seen 

 that in the majority of cases solutions varying from 2 per cent, 

 to 5 per cent, have proved strong enough. As changes in the 

 appearance of the protoplasm follow slowly upon its contraction, 

 the time at which certain appearances are presented is usually 

 given. The following are the details of the experiments : 



Prothallus of Nephrodium villosum and Aspidium 



FiLIX-MAS.J 



On treating a prothallus of either of the above specie? (others 

 have not been examined) with a 2 per-cent. solution of common 

 salt, the protoplasmic body in each cell is seen to separate itself 

 gradually from the cell wall, the process beginning as a rule 

 at the corners of the cells. The contraction goes on slowly for 

 a considerable time, and usually results in the protoplasmic 

 body assuming a more or less regular spherical form, as has 

 been frequently described by former writers. When stronger 

 solutions are used the contraction is more rapid but usually 

 less regular. 



When the protoplasm first contracts in this way there is 



