36 WHEAT RESISTANCE TO TOXIC SALTS. 



Magnesium sulphate aud mao-uesiuni elilorid (litter l)ut little in the 

 concentration necessary to kill the root tips of wheat seedlings, while 

 a solution of the former only half as strong as the latter is sufficient 

 to kill the lupines in the same length of time. In contrast to this, a 

 solution of magnesium chlorid only about one-third as concentrated as 

 the critical solution of magnesium sulphate is the strongest that can 

 be endured by the root tips of maize, the order of toxicity of the two 

 salts being reversed. The root tips of the lupines have been killed 

 by every salt used, at a less concentration than that which can be 

 endured by wheat and maize, a solution of sodium carbonate one-half 

 and one-third as concentrated as that necessary to kill wheat and 

 maize, respectively, being fatal to the lupine. It will be noticed, 

 however, that the least amount of diversity is evinced by the three 

 plants in the presence of sodium carbonate and sodium bicarbonate. 



Wheat and maize show very little ditference in resistance to sodium 

 sulphate, but a solution about one-sixth as concentrated as that neces- 

 sary to kill maize is toxic to the lupine. 



It is a very surprising fact that the variation between the three 

 plants is so great. The salts of magnesium wdiich are the most toxic 

 to wheat and lupines are the least toxic to maize, the ditference being 

 as is 200 to 1. Maize is on the whole much more resistant to pure salt 

 solutions than is wheat or the white lupine, while the root tips of the 

 lupines are killed by each of the salts at a much less concentration 

 than that necessary to destroy the root tips of wheat seedlings. 



Especially interesting results in this connection have been brought 

 out by Cameron and Breazeale " with some experiments concerning 

 the action of acids and salts upon maize, wheat, and clover. The 

 salts employed were not the same as those used by the writer, but the 

 results for both the acids and salts are sufficient to show the dilTci-ence 

 in resistance betAveen dilferent species and also the different action of 

 ditferent salts and acids on the same species. 



Cameron and Breazeale found that N/850 and N/GOO solutions of 

 acetic and succinic acids, respectively, were the toxic limit for seed- 

 lings of maize, but wheat and clover in the same acids would endure 

 only N/20000. They found the variations in salt solutions to be 

 equally as great, but in some ways reversed. In potassium chlorid the 

 toxic limit for wdieat and clover is the same, each having a greater con- 

 centration than that necessary to kill seedlings of maize. In potassium 

 oxalate, wheat was found to endure a concentration six times as great 

 as that for clover. It is interesting to note here that the more toxic 

 the acids the more uniform are the results, while for the salt solutions 

 the reverse is true. The writer obtained similar results for the salts 

 used in the experiments described in this paper. 



a The Toxic Action of Acids and Salts on Seedlings, Journal Phys. Chem., vol. 

 8, No. 1, p. 1 (January, 1904). 



