214 INJURY, RECOVERY, AND DEATH 



may be the additional injury due to the toxic action of 

 the salt. For this reason many cells which would recover 

 if very slightly plasmolyzed may not do so if plasmolyzed 

 more strongly, since recovery may require so long a time 

 that the process of injury gets the upper hand. 



It was found that recovery was more rapid in NaNOo 

 than in a balanced solution of NaNOg + Ca(N03)2 or in 

 Ca(N03)2 alone. Similar experiments with RbCl, CsCl, 

 and CaClj gave the same result. This indicates that in a 

 solution of NaNOg, NaCl, EbCl, or CsCl penetration is 

 more rapid than in Ca(N03)2, CaClg, or in a bal- 

 anced solution. 



These results agree with those obtained in the study 

 of Spirogyra?^ 



The experiments on conductivity were carried out by 

 means of the apparatus described on page 34. As it was 

 desirable to surround the cell by a solution of the same 

 conductivity as that of the cell sap determinations of the 

 latter were made by filling a small tube with sap and 

 inserting an electrode at each end (taking great care to 

 avoid the inclusion of air bubbles). It was found that 

 the sap had approximately the conductivity of sea water 

 plus three parts of distilled water (this will be called 

 for convenience 0.25 sea water). The cells were accord- 

 ingly placed in this for some time before beginning the 

 determination of the conductivity of the living cell. 

 Under these circumstances it was assumed that altera- 

 tions in conductivity during the course of the experiment 

 must be due (in great part at least) to changes in the 

 protoplasm, rather than in the cell sap. 



In general, it was found that in 0.25 sea water, the 

 resistance remained unaltered for a long time, while in 

 NaNO,, of the same conductivity it soon began to fall. 



^ See page 201. 



