372 



FLOYD JOHN BRINLEY. 



as before, by a borax buffer. Leaves of Elodea near the growing 

 tip of the branch were placed in a solution of hydrogen cyanide 

 in Syracuse watch glasses and the time noted when the streaming 

 of the protoplasm ceased. The results of a typical set of experi- 



30 



CO 

 LJ 



I- 

 D 



20 



10 







6 7 

 PH 



8 



FIG. 5. Curve showing the effect of pH on the streaming of protoplasm 

 in Elodea cells. Abscissae represents pH ; ordinates time in minutes re- 

 quired for streaming to stop. 



merits are plotted in Fig. 5. Again the results show that the 

 streaming of protoplasm stopped first in solutions of the same pH 

 values in which HCN penetrated the artificial frog skin " cell " 

 most quickly. Thus, in determining the toxicity of hydrogen cya- 

 nide to any organism, the value of controlling the hydrogen ion 

 concentration of the solution is apparent. 



