of NaCl, l'gCl2, I'gS04, KCl and CaClg is necessary for the 

 best growth of marine algae. True and Eartlett* in an ex- 

 tended research have brought out the fact that a ratio of 

 one molecule of calcium to 9 molecules of magnesium inhibits 

 the toxic effect of rather high concentrations of magnesium 

 upon roots of Canada field peas. Other cases of antagonis- 

 tic salt action in combinations of salts of the alkali r.et- 

 als or of the alkaline earths have been demonstrated, and 

 some information has been obtained regarding the influence 

 of these salts on the effect of the heavy metals, which are 

 almost universally toxic. The heavy metals have not received 

 so r.uch attention , however, and it seemed worth while to in- 

 vestigate some of these alone and in the presence of calcium 

 and magnesium, to obtain evidence as to whether the lighter 

 metals may modify an any way the toxicity of the heavy met- 

 als . 



The investigation described in this paper was ac- 

 cordingly undertaken. The problem here involved will be tak- 

 en up more in detail aft-r some of the literature pertinent 

 to this investigation has been considered. 



One of the earlier investigations on the influence 

 of chemical compounds on the toxicity of the heavy metals 



4. True, R. H., and Bartlett, H. H., Absorption and excret- 

 ion of salts '.s influenced by concentration and composition 

 of culture solutions, U. S. Dept . of Agr., Bur. Plant Ind. 

 Bulletin Ko. 231, 1512. 



