174 INJURY, RECOVERY, AND DEATH 



salts. We may assume tliat they may act upon the 



hypothetical substance M, and increase its resistance by 



changing properties other than the thickness of the layer. 



In order to ascertain whether these results have gen- 



Per cenc 

 lOOi 



NaCl 

 CaCl2 



Fio. 76. — Curves showing antagonism (after an exposure of 24 hours) between NaCl 0.52 

 M and CaCla 0.278 M in Laminaria agardhii (upper curve) and Rhodymenia palmata (lower 

 curve). ^ The ordinates denote net electrical resistance. The abscissse denote molecular 

 proportions of the solutions (all the solutions having the conductivity of sea water). Thus 

 NaCl 85, CaCli 15 signifies a mixture of 75 c.o. NaCl 0.52 Jlf + 25 c.c. CaCh 0.278 M in which 

 the molecular proportions 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%. Average of six experiments. Probable error of the 

 mean less than 5.2% of the mean. 



eral validity, experiments were made upon other plants 

 and upon animals. In general the outcome (as far as the 

 experiments have gone) is similar to what has been 

 described for Laminaria. Thus antagonism between 

 NaCl and CaClj was observed in the cases of Ulva (sea 

 lettuce), Rhodymenia (dulse) and Zostera (eel grass).*^ 

 As was to be expected, the most favorable proportions 

 were not always exactly the same for the different plants. 



"Osterhout (1919, A). 



