[Vol. 2 



482 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



position of vegetable matter in the soil, as pointed out by 

 Schreiner and Reed ('07) and others, it is not believed that 

 in the case under consideration the oxidizing power of the 

 roots was altered to any appreciable degree by the boiling of 

 the medium. Dachnowski ('12) mentions the effect of oxida- 

 tion upon the toxic substances found in bog water. In the 

 sterilization method by boiling under a return condenser, 

 however, the aeration or oxidation phenomenon would no 

 doubt play only a subsidiary role. The stronger line of evi- 

 dence seems to favor the destruction of injurious bacterial 

 and fungous agencies as the chief factor in the beneficial 



O v "" *•*© 



effect of the sterilization. 



VII. Conductivity Measurements 



The excellence of the electrical conductivity method for 

 determining any change in the electrolyte content of an 

 aqueous medium naturally led to its adoption for the experi- 

 mental work described below. This phase of the investiga- 

 tion was especially concerned with determinations pertaining 

 to the extraction of electrolytes — including the essential 

 nutrient salts — from the roots of plants in distilled water. 

 The generally beneficial results attendant upon a frequent 

 renewal of the distilled water in which the plants were placed 

 has already been noted, as well as the evidence in favor of 

 the view that conditions other than extraction of essential 

 salts constitute the underlying cause of the deterioration of 



plants in distilled water. 



The next point to be determined was the relative amount 

 of the total exosmosis in the renewed distilled water as com- 

 pared with that in the unrenewed. In placing roots in dis- 

 tilled water it is pertinent to this subject to inquire whether 

 all the exosmosis occurs during the first four days. If it does, 

 we should have the same amount of extraction in both the 

 unrenewed water and that renewed every four days. Or is 

 there a renewal of the exosmosis of the electrolytes follow- 

 ing the renewal of the water each time, thereby giving rise 

 to a greater exosmosis than in the cultures in which the water 

 was not renewed? If such a condition obtains and yet in 



