136 M. M. McCooL 



portion of magnesium in cultures with calcium salts or with full nutrient 

 solutions (lacking magnesium), is unimportant during the first two weeks 

 of growth. These results are in agreement with those obtained by Konig 

 and Haselhoff (1894). These investigators found that LeguminoscB endure 

 the lack of potassium better than the lack of calcium. 



Numerous data have been brought forward which seem to show that a 

 more or less definite ratio of calcium to magnesium is beneficial for plants. 

 Many of the reports in which these data are embodied have been sum- 

 marized. A further study of the antidotal relations that exist between 

 these bases in full nutrient solutions is interesting and important. Canada 

 field pea seedlings were grown in nutrient solution cultures containing 

 calcium and magnesium in various proportions. The nutrient solution 

 that was used as the solvent for these bases in series 1 was made up as 

 follows : 



Ca(N03)2 4.00 grams 



KH2PO4 1 .00 gram 



KNO3 1.00 gram 



MgS04 1 .00 gram 



KCl 0.50 gram 



FeCls 0.01 gram 



Distilled water 3 . 00 liters 



No considerable antagonistic action is evident from cultures made up 

 as were those in this series, inasmuch as the quantities of calcium and 

 magnesium employed are not to be considered toxic under the conditions. 

 However, a slight increase of growth ensues when either calcium or mag- 

 nesium is added to the nutrient solution, but in general this is not so exten- 

 sive as in the cultures to which both are added. The data obtained from 

 this set of experiments appear in Table 2. 



In this table toxicity is not evident, although the addition of calcium 

 chlorid alone or calcium and magnesium together causes increased growth 

 over the control (full nutrient alone) . It may be that the full nutrient 

 solution (Pfeffer's) is not a properly balanced solution for Canada 

 field pea. 



The nutrient solution employed in the second series of experiments 

 (Table 3) was one tenth as strong as that in the preceding cultures. 



