188 



M. M. McCooL 



Full nutrient solution also was employed as a medium in which to 

 grow seedlings for the first ten days. The plants were then placed in 

 cultures containing calcium and manganese separately, and in cultures 

 in which these metals were both in solution. (Precautions were taken to 

 wash carefully the roots of the seedlings when they were removed from 

 the nutrient solution.) Final notes were made twenty days later. The 

 total and the average length of both tops and roots of these plants are 

 greater than in those that were grown for the first ten days in distilled 

 water and then transferred to solutions of calcium and manganese. Here 

 again calcium ions are effective in antidoting manganese ions. 



TABLE 8. Experiment Continued for Twenty Days 



. Data for 



Ten Plants 



Previous condition of 

 growth 



Composition of 

 solution 



Total 



green 



weight 



(grams) 



Average 

 length 

 of tops 

 (centi- 

 meters) 



Average 

 length 

 of roots 

 (centi- 

 meters) 



Ten days in full nutrient 

 solution 



N/10 CaCU 



N/10 CaCl2+N/50 



MnCU 



N/10 CaC]2+N/100 



MnCl2 



N/10 CaCl2+N/200 



MnCU 



N/100 MnCl2 



N/200 MnCla 



Distilled water 



18.85 



10.35 



11.42 



16.55 

 No further 



growth 

 Very slight 

 growth 

 11.95 



24 



20 



22 



25 

 Dead 



14 



11 



9 



11 



10 



8 



It may be concluded, from the data obtained from the two series of 

 experiments, that the nature of the substratum (that is, whether distilled 

 water or nutrient solution) in which the seedlings were grown for the first 

 ten days does not influence markedly the antidotal relation of calcium to 

 manganese. 



Calcium and manganese {full nutrient solution) . — Data have been pre- 

 sented which establish the fact that manganese is much less toxic with 

 respect to seedlings in full nutrient solutions than to seedlings in distilled 



