MISCELLANEOUS 



417 



Figure 167. Ordinates show the pH values of the external solution when 25 grams 

 of tissue were immersed in 25 cc of various salt solutions of the concentrations shown 

 as abscissae. In the graph for rye seeds the salts listed in the shaded areas gave similar 

 results, all the data for these salts falhng within the limits shown. Note that each tissue 

 did not bring the external solution to definite pH values, but that the values obtained 

 varied with the salt used, with the concentration of the salt, and especially with the 

 nature of the cation. 



reached varies with both the concentration of the solution and the nature 

 of the cation, which means that pH was not constant and could not repre- 

 sent the isoelectric points of the living cells. All these findings are shown 

 by Fig. 167 for potato tissue and rye seeds. It will be noted that high 



