142 



M. M. McCooL 



From an examination of the preceding table it is clear that a toxic solu- 

 tion of KCl strong enough to kill, N/20, may be rendered harmless by 

 an equal quantity of calcium; while if the solution contains N/500 CaCl2 

 to N/20 KCl, the maximum effect of calcium addition is not felt. On the 

 other hand, with the maximum strength of the calcium salt employed, 

 dilution of the KCl to N/500 does not materially affect growth as com- 

 pared with that in the strongest combined concentrations employed. 

 Inasmuch as the solutions containing calcium alone yield more growth 

 than does the distilled water culture, the increase in growth of the plants 

 in the combined solution over that in the solution of calcium alone should 

 not be attributed wholly to the protective action of potassium with respect 

 to calcium. 



TABLE 8. Experiment with Wheat. Duration, Thirty Days. 



Plants 



Data for Ten 



Composition of solution 



N/100 CaCl-2+N/lOO KCl 

 N/100 CaCl..+N/200 KCl 

 N/lOO CaCl2+N/400 KCl 



N/100 CaCU 



N/100 KCl 



N/200 KCl 



Distilled water 



Total 



green weight 



of plants 



(grams) 



2, 



2. 



2. 



2. 



1. 



2.20 



1.71 



Average length 



of tops 



(centimeters) 



12.5 

 12.5 

 12.3 

 27.5 

 7.0 

 7.5 

 17.5 



Average length 



of roots 



(centimeters) 



12.5 

 15.2 

 15.0 

 17.5 

 9.5 

 11.5 

 10.0 



From a consideration of Table 8 it is seen that a solution of N/100 

 KCl is toxic for wheat seedlings (and it should be noted that a concentra- 

 tion of N/50 KCl practically prohibits growth) ; and this effect is to a 

 considerable extent prevented by the addition of an equal quantity of 

 calcium. Nevertheless, in the combined solution there is not so great 

 a growth of tops as in the calcium alone, nor is the growth of tops in 

 the combined solution quite so great as that in distilled water. With 

 respect to wheat the experiments are not sufficient to determine whether 

 or not there is a protective action of potassium toward calcium, since 

 a toxic solution of the calcium salt was not employed. 



