8 GROWTH OF WHEAT SEEDLINGS. 



thus clearly showing the selective ability which roots possess to take 

 up one part or radical of a salt and to leave the other. All of this 

 chlorin did not exist as hydrochloric acid, for after boiling and 

 titrating with twentieth-normal sodium hydrate, using phenolphtha- 

 lein as an indicator, a reading equivalent to only 14.6 parts per 

 million of hydrochloric acid was obtained, which, however, is a 

 much larger amount of free acid than was originally present in solu- 

 tions 9 and 10, where only 10 parts per million of acid were used. 



The effects of the strongly acid solutions were markedly shown 

 upon the roots, that is, in the potassium-chlorid solution they showed 

 the same general characteristics as those grown in the hydrochloric 

 acid; they were short, stubby, and often discolored, the tips being 

 enlarged, and many of the roots growing in the shape of a fishhook, 

 a characteristic of roots grown in the presence of some toxic sub- 

 stance. Moore, Roaf, and Knowles, 1 as a result of their investiga- 

 tion, found that the smallest amount of free acid arrests the growth 

 and nuclear divisions at the root tip, causing it to become thicker, 

 while dilute alkali stimulates the tip to excessive nuclear division. 



Of the 10 parts per million of hydrochloric acid added to solution 

 9, only 1.8 parts remained in solution after the first cropping. The 

 remainder was either absorbed by the plants or the carbon black, 

 or was neutralized by the aluminum disk. Both in the case of the 

 potassium chlorid and of the hydrochloric acid, the presence of 

 calcium carbonate overcame the injurious effects of the acids in the 

 solutions. That is, of course, a common observation and hardly 

 requires citations from the literature to substantiate it. Claudel and 

 Crochetelle 2 found that when they used ammonium sulphate, potas- 

 sium chlorid, or potassium sulphate in amounts varying from 500 

 to 5,000 parts per million, an injurious action on germination was 

 noted, and that the application of lime neutralized this toxic effect. 



The results obtained by the use of lime in the experiments here 

 reported can be explained only by assuming that the lime has been 

 used to neutralize the acids. 



Effect of reaction of the solution on weight of roots and tops. 

 In making the culture medium alkaline, the growth of the root has 

 been most favorably affected. From Table 2 it is seen that in every 

 case where lime was present the weight of the roots was greater than 

 in the corresponding case without lime, and especially was this so 

 where hydrochloric acid and sulphuric acid had been used, with and 

 without lime. 



1 Effects of Variations in Inorganic Salts and the Reactivit}' of the External Medium 

 upon the Nutrition, Growth, and Cell Division in Plants and Animals. Biochem. J., 

 1908, S:279. 



2 Les engrais et la germination. Ann. Agron., 1896, 22: 131 



