194 THE BOTANICAL MAGAZINE. [v.,i. xxvu. No. 322. 



salts, even though each component is present in an amount 

 that is toxic in pure solution. A mixture of the more important 

 salts present in sea water, each at about the concentration at 

 which it occurs in the sea, was found to be the best medium 

 for the growth of marine alga. Moreover, the same phenome- 

 non has been observed also even in the case of land plants. 



Kearney and Harter 1 ' also investigated the neutralizing 

 effect of calcium sulphate upon the toxicity of magnesium and 

 sodium salts with eight different land plants and found that 

 the presence of calcium sulphate tends very greatly to diminish, 

 not only the differences between different species as to their 

 tolerance of magnesium and sodium salts, but also the diffe- 

 rences between the latter in their toxicity to the same species, 

 and the neutralizing effect of calcium sulphate is generally much 

 more marked with the magnesium than with the sodium salts. 



In 1907, Benecke 2j also studied the poisonous action of 

 various salts upon the growth of spirogyra. The result of his 

 investigation was summarized as follows : chloride, nitrate, 

 sulphate and phosphate of sodium, potassium, magnesium and 

 iron are more or less poisonous, and among these cations iron 

 and magnesium are more poisonous than potassium, sodium is 

 less poisonous than potasium ; among the anions, chlorine is 

 least poisonous. The toxicitjr of these anions and cations can 

 be neutralized or decreased by the addition of calcium ion. 

 Loew and Aso 3; also studied the same subject in relation to 

 spirogyra and observed that calcium salt can prevent the toxic 

 effects of magnesium salts while potassium salts can retard but 

 not entirely prevent the injurious action of the same. 



Takeuchi 4) has pointed out, at the end of his investigation 

 on the behavior of algae to salts at certain concentration, that 

 the injurious action of magnesium salts can only completely be 

 overcome by calcium salts, and not by sodium or potassium 



L) Bull. No. L13, Bureau of Plant Industry, U.S. Dept. of Agriculture 



2) Ber. d. D. Bot. Ges., Bd. 25, p. :!22 (1907). 



3) Bull. Coll. Agric., Tokyo [mp. Univ., Vol. 7, pp. 395 409(1906 L908). 

 ■I. Bull. Coll. ^gric, Tokyo [mp. Univ., Vol. 7, p. 628 (1906-1908). 



