280 



DETERMINATIONS OF PERMEABILITY 



The conductivity was first determined in 0.25 sea water, this was 

 then replaced by another solution of the same conductivity. The 

 conductivity in the new solution was then determined at intervals. 



In general it was found that in solutions in which the cells lived 

 well, such as dilute sea water or a balanced solution of NaNOs plus 

 Ca(N03)2, the resistance did not fall. But in solutions in which 

 injury occurred, such as NaNOs, the resistance fell. In Ca(N03)2 

 and in CaCh there was a rise in resistance followed by a fall. 



Fig. 1. Apparatus for measuring the conductivity of Nitella. The cells {N) 

 are placed in a trough in a block of paraffin (P) and covered with a glass plate (G). 

 The solution is poured in through the funnel (T) and runs out through the open- 

 ing (0). At E and E are platinum electrodes. 



These experiments agree with those made on Laminaria except 

 that the rise observed in Ca(N03)2 or in CaCl2 was often smaller 

 in the case of Nitella. This, however, is not unexpected, since the 

 concentration of CaCl2 was only one-fourth of that used in the 

 experiments on Laminaria. It may be added that the rise observed 

 in CaCl2 differs greatly in different organisms. In Rhodymenia,^'^ 



I'Osterhout, W. J. V., J. Gen. Physiol., 1918-19, i, 299. 



