1915] 



MERRILL ELECTROLYTIC DETERMINATION OF EXOSMOSIS 



563 



over on the roots from the full nutrient solutions, salt solu- 

 tions, and other media to the distilled water, at least not in 

 sufficient quantity to affect the validity of the results in any 

 way. Although the conductivity of the acid and alkaline 

 media was very high, it is seen by reference to table xv that 

 after rinsing the roots in the usual manner and transferring 

 the cultures to distilled water the readings were very low, 

 thus showing that practically no electrolytes were carried 

 over on the roots. 



TABLE XV 



CONDUCTIVITY READINGS OF THE CULTURE MEDIA OF PLANTS IN KOH, H1SO4, 



AND LATER IN DISTILLED WATER 



Cult. 



no. 



Specific conductivity* 



> 



OF THE SOL NS, 



Values of jc,t or 



BRIDGE READINGS OF THE 

 DISTILLED WATER 



Treatment 





QJ 





1 



2 



3 



4 

 5 



N/12,800 H.SCX, 

 47 hrs 



N/6,400 H,SO<, 

 47 hrs 



N/400 KOH, 47 

 hrs 



N/200 KOH, 47 

 hrs 



u 



o 



cq.S 





<.a 



2.39 1.50 



5.62 

 42.02 



2.53 



to • 



u - 



o 



CO 





1.03 

 1.17 



u 



CO 



C4 



u 





<.s 



- 



-1.36 

 -4.45 





C0 



X 



— s 



0) 



CO ^ 

 U CO 



a 



0) CO 



c 



10.8 10.5 



8.7 



9.6 



4.8 

 2.7 



-.3 

 .9 



to 



CO 



rt Si 



o 



20.09 16.39 



Control (dist. H2O, 

 not changed) . . . 



58.50 27.98 24.16 



-25.63 11.5 8.7 5.5 



-34.34 



.98 





2.56 1.32 



.34 



11.2 



22.8} 



10.5 



** 



5.2 



17.816.8J 



-2.8 

 -.7 



-5.0 



4.5 

 3.6 



2.7 



4.5 



* * 



11.8 



* The values given are to be multiplied by 10"" 6 . 

 t The resistance in the box was 9,110 ohms. 

 t After being in distilled water 47 hours. 



ft The average reading of the distilled water before placing roots in it was 

 approximately 6.0. 

 ** After 97 hours. 



IX. General Discussion 

 In the foregoing experiments we have been able to note the 

 exosmosis of electrolytes following different treatments. As 

 compared with the controls we have seen marked excretions 

 in some cases and slight or no exosmosis in excess of that in 

 the controls in others. In the normal untreated cultures, or 

 controls, we have seen that there is almost universally a slight 

 exosmosis from the roots into the distilled water for about 24 



