Relations of Manganese and Other Cations 185 



lings in culture 3 became chlorotic after a short time and few remained 

 alive until the close of the experiment; whereas those in culture 4 were 

 uninjured and the stems were far less corroded than those in culture 2. 

 A comparison of the plants grown in culture 6 with those in the control, 

 culture 8, discloses the fact that the toxicity of N/100 MnCl2 toward 

 seedlings grown in the dark is very slight. On the other hand, the 

 toxicity of manganese in ordinary greenhouse light is appreciated when 

 one compares the development of the plants in culture 5 with that in 

 culture 7. The writer is not prepared to offer an explanation of the cause 

 of these results. 



An examination of the data in the preceding table and of Fig. 10 further 

 emphasizes the fact that the toxicity of manganese is manifested mainly 

 toward the tops of the plants. The injury to the roots is inappreciable 

 in all the above cultures except 1, 2, and 3. The increased toxicity of 

 manganese in plants grown in light may be due to the greater accumu- 

 lation of manganese in the leaves, this being brought about by greater 

 transpiration. 



Antidotal relations of calcium, potassium, sodium, and 7nagnesium toward 



manganese 



In a previous paper the writer has summarized some of the more 

 important data regarding the antitoxic relations of various mineral ele- 

 ments as cations. He has also added the results obtained from many of 

 his experiments. In connection with the studies on manganese, the 

 writer has investigated the antidotal relations that exist between this 

 element and each of the following: calcium, potassium, sodium, and 

 magnesium. 



Calcium and manganese 



Calcium and manganese {distilled water) . — By means of several series 

 of experiments it has been definitely proved that manganese is rendered 

 innocuous by the addition of calcium. It is to be noted, for example, 

 that a pure solution of N/4000 MnCls is toxic to seedlings, but when a 

 stronger solution, N/1000 MnCls, is mixed with N/2000 CaCla the injury 

 due to the manganese is greatly reduced. Protective action exists also 

 with various other combinations of calcium and manganese. The data 

 obtained are set forth in Table 6: 



