196 



M. M. McCooL 



Sodium and manganese 



Sodium and manganese (distilled water). — Sodium and manganese are 

 mutually antagonistic in distilled water. Solutions of N/50 NaCl reduce 

 the poisonous action of solutions of manganese ranging in concentration 

 from N/500 to N/5000. The toxicity of both sodium and manganese 

 toward wheat seedlings is not evident when the salts of these metals are 

 present in solution as N/50 NaCl +N/ 5000 MnCl2, and the amount of 

 injury is greatly lessened in the other combinations employed. The data 

 obtained are summarized in Table 14: 



TABLE 14. Experiment with Wheat, Continued for Thirty Days. Data for Eight 



Plants 



Composition of solution 



Total weight 

 (grams) 



Average length 



Average length 



of tops 



of roots 



(centimeters) 



(centimeters) 



2.0 



1.0 



5.5 



2.0 



6.0 



8.0 



9.0 



9.0 



1.0 







3.0 



2.0 



4.0 



3.0 



9.0 



4.0 



N/50 NaCl + N/500 MnCh. . 

 N/50 NaCl +N/ 1.000 MnCU 

 N/50 NaCl+N/3,000 MnCh 

 N/50 NaCl+N/5,000 MnCU 



N/50 NaCl 



N/3,000 MnCU 



N/5,000 MnCU 



Distilled water 



0.36 

 0.80 

 0.90 

 0.92 

 Very slight 

 0.48 

 0.55 

 0.92 



Magnesium and mangafiese 



Magnesium and manganese (N/IOOO CaCk). — The fact that magnesium 

 and manganese are very toxic in pure solutions makes it especially interest- 

 ing to ascertain the results when these are combined. The development 

 of pea seedlings is greater in cultures containing both these harmful sub- 

 stances than in cultures in which only one is present, again indicating 

 mutual antagonism. N/500 and N/1000 MnCl2, for example, are injurious 

 to the tops. This injury is prevented by the presence of N/50, N/100, 

 or N/200 MgCl2; moreover, the development of the plants in these solu- 

 tions is more extensive than in the corresponding solutions of magnesium. 



Magnesium and manganese (Jull nutrient solution) . — In this series, as 

 in the preceding one, ma'gnesium effectively counteracts the injurious 

 action of manganese toward pea seedlings. It is to be noted, for example, 

 that solutions of N/200 MnCl2 are very toxic; the leaves of seedlings 



