CONDUCTIVITY AND PERMEABILITY 209 



the slower rate of recovery in MgClg, CaClj, AI2CI0 and 

 Ce (N03)3 shows that in these salts penetration is slower 

 than in the balanced solution. 



This is in complete agreement with the results of the 

 electrical experiments (even the order of penetration of 

 the salts of Mg, Ca, Al and Ce, is the same as that found 

 by the electrical method). 



10 ZO JO 50 70 fo r||iiute> 



Fia. 92. — The ordinates denote rate of recovery from the effect of hypertonic solutions of 



strips of the peduncle of the Taraxacum officinale. The rapid rate of recovery in NaCl, 



KNOi and NHiCl shows rapid penetration of these salts. On the other hand in MgCli, 



CaCli, AlzCIe and Ce (NOt)a penetration is slower than in the balanced solution. 



Eeeently the writer has had an opportunity to test 

 some of these conclusions by direct determinations of 

 the penetration of substances into the cell sap. The 

 advantages of this are obvious, ,when we consider the 

 uncertainty of most indirect methods. 



Some investigators have sought to avoid the diffi- 

 culties of indirect methods by making analyses of tissues, 

 but these must obviously include too much intercellular 

 material to be satisfactory. Analysis of the solutions 



14 



