356 



Journal of Agricultural Research voi. xvni. No. ^ 



This same experiment was twice repeated, using sodium sulphate 

 instead of sodium chlorid, with the results shown in Table III. 



Table III. — Analyses of loo whole plants 



Concentration of solution. 



Distilled water 



4,000 p. p. m. of sodium sulphate 



4,000 p. p. m. of sodium sulphate + 30 p. p. m. of cal 

 cium oxid 



Sodium 

 sulphate. 



Gm. 

 Trace, 

 o. 0219 



.0521 



The results with sodium sulphate are even more striking than those 

 with sodium chlorid. Instead of hindering the absorption of sodium 

 sulphate by the plant, the calcium oxid actually stimulated it. Even 

 when calculated upon the basis of grams of dry weight, there is still a 

 preponderance of sodium sulphate in the plants grown in the presence 

 of the small amount of lime. 



CONCLUSIONS 



(i) The higher tolerance to alkali salts shown by plants in soil and 

 sand than by those grown in water cultures is not due entirely to the 

 physical effect of the presence of solid particles of different degrees of 

 fineness, but also to certain soluble substances which are sometimes 

 present in very small quantities. 



(2) Very small amounts of calcium oxid and calcium sulphate overcame 

 the toxic effects of sodium chlorid and sodium sulphate. 



(3) Magnesium sulphate and barium chlorid were slightly antagonistic 

 to sodium chlorid. Potassium chlorid, sodium nitrate, sodium phosphate, 

 ferric chlorid, and alum had no effect on the toxicity of sodium chlorid. 



(4) Within the limits of our experiments the presence of lime did not 

 prevent the entrance of sodium chlorid and sodium sulphate into the 

 plant cells. The antagonistic effects of lime would seem to be due not 

 to its effect on the permeability of the cells but to some other cause. 



