124 BOTANICAL GAZETTE [February 



need merely say that it cannot be true because this inhibitory action 

 is seen in mixtures of potassium nitrate and magnesium nitrate where 

 no double salt is formed. Moreover, even in the chlorids and suKates 

 the formation of a double salt cannot much affect the result, since the 

 double salt, at the concentrations here used, dissociates and sets free 

 magnesium and potassium ions to almost the same extent as the 

 simple salts. 



RESULTS 



Magnesium salts and potassium salts, used separately, are poison- 

 ous to plants, but when mixed together (in suitable proportions) the 

 poisonous effects more or less completely disappear. These results 

 are of importance in soil investigations. 



University of California 



Berkeley 



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