348 PENETRATION OF CATIONS INTO LIVING CELLS 



The cells were placed in the solutions^ for various lengths of time. 

 When they were taken out they were thoroughly rinsed in running 

 tap water, dried with filter paper and pierced with a fine pointed 

 capillary pipette, which collected the cell sap in a very satisfactory 

 manner. This was tested by means of the spectroscope. 



The normal cell contained Na, Ca, and CI; for this reason Na and 

 Ca were not used in making up the test solutions. 



The cations used were Li, Cs, and Sr. In order to avoid plasmoly- 

 sis hypotonic solutions were employed. 



In order to make sure that the tests obtained were not due to small 

 quantities of the solution adhering to the outside of the cell, cells 

 were placed for half an hour or longer in each solution, taken out, 

 washed in running water, and tested in the usual manner. The test 

 was in all cases negative, showing that the method as ordinarily used 

 excludes errors due to contamination. 



When Nitella was placed in 0.05 m LiCl, penetration of Li could be 

 demonstrated in 24 hours. At this concentration the salt was not 

 toxic. The cells remained in good condition for 4 days (after which 

 the experiment was discontinued). Other plants which had been 

 placed in 0.025 m LiCl gave a faint test for Li in 48 hours and were 

 found to be in excellent condition at the end of 13 days. 



In a balanced solution of Li (containing 10 parts 0.04 m LiCl, 9 parts 

 tap water, and 1 part sea water) the cell sap gave a good test in 48 

 hours and cells were found to be in excellent condition at the end of 

 16 days. 



Other cells were placed in 0.05 m CsCl and gave a good test in 24 

 hours. These were under observation for 6 days, during which time 

 they remained in good condition. 



In a balanced solution containing 10 parts 0.05 m CsCl, 9 parts tap 

 water, and 1 part sea water, the cell sap gave a good test for Cs in 

 3 days, and the cells remained in good condition for 4 days (after 

 which the experiment was discontinued). 



In SrCl2 (0.075 m) Nitella remained alive for 20 days, and there was 

 a slow penetration requiring 3 days or more to give a good test. The 



•The solutions were approximately neutral. The temperature did not vary 

 much from 19°C. 



