W. J. V. OSTERHOUT 



303 



One of the most interesting experiments on Laminaria consists in 

 placing it first in NaCl (causing a fall in resistance) and then in 

 CaCl2, causing a rise. In this way rapid changes of permeability may 

 be produced and the alternation may be continued for a considerable 



Per cent 

 lOO- 





 100 



Fig. 2, Curves showing antagonism (after an exposure of 24 hours) between 

 NaCl 0.52 M and CaCl2 0.278 m in Laminaria (upper curve) and Rhodymenia 

 (lower curve). The ordinates denote net electrical resistance expressed as per 

 cent of the normal resistance in sea water (which is taken as 100 per cent). The 

 abscissae denote molecular proportions of the solutions (all the solutions having 

 the conductivity of sea water). Thus NaCl 85, CaCl2 15 signifies a mixture 

 of 75 cc. NaCl 0.52 m + 25 cc. CaCla 0.278 M in which the molecular propor- 

 tions of Na to Ca are as 85 to 15. Temperature 17.5° ± 5°C. During the 24 

 hours the resistance of Laminaria in sea water remained practically unaltered 

 while that of Rhodymenia fell to 84.5 per cent. Average of six experiments. 

 Probable error less than 5.2 per cent of the mean. 



