1908] OSTERHOUT— ACTION OF MAGNESIUM AND POTASSIUM 121 



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1 



Turning now to the experiments with sulfates and nitrates, we 

 see entirely similar results, save that the mixed solutions, while better 

 than pure magnesium salts, 

 are not better than pure potas- 

 sium salts. The question 

 might then arise whether the 

 favorable result is due in this 

 case to mere dilution of mag- 

 nesium salts with less poison- 

 ous ones. This, however, is 

 not the case. We are dealing 

 with a true antagonistic action. 

 This is shown by the fact that 

 addition of the potassium salt 

 in solid form likewise pro- 

 duces a favorable result, and 

 also by the fact that the 

 addition of pure water does 

 not produce anything like 

 the improvement seen on the addition of the same amount of a 

 solution of a potassium salt. 



.0937 m 



Fig. 2. — Growth of wheat roots during 

 40 days in .0937W solutions: I, MgClj, 

 aggregate length of roots 10™"*; 2, ioqcc 

 KCl + 25CC MgCU, aggregate length of roots 

 153™™; 3) KCl, aggregate length of roots 



.05m- 



,0S7&m 



d 



a c 



Fig. 3. — Curves showing growth of wheat roots in salt solutions. The ordinates 

 represent concentrations (parts molecular); the abscissae represent the aggregate 

 length of roots per plant in millimeters, a, loocc KCl+ioocc MgCU; &, ioqcc KCl 

 + 50CC MgClj; c, KCl; d, ioqcc KCI + 25CC MgClj. 



