ISIEUTKALIZING EFFECT OE SALTS EMPLOYED. 31> 



variety Avitli both the chlorid iukI the sulphate of inagiiesium is 

 O.OOa iiorinal. In both salts, however, rootlets of some of the plants 

 survived in solutions twice as concentrated. In the case of magne- 

 siuui chlorid, 8 out of 25 survived, while with the sulphate only 2 

 out of the same number survived. 



Kharkof. — In solutions of sodium chloi-id and sodium sulphate of 

 a concentration of 0.045 and 0.085 normal, respectively, one seedling 

 of the Kharkof variety was dead in each, the limits fixed for these 

 two salts being 0.055 and 0.0425. The root tips of two seedlings were 

 killed in 0.02 normal of sodium bicarbonate, for which the average 

 toxic limit is 0.03. 



Z'nnmeA^man. — The Zimmerman variety, while the most resistant of 

 all, shows some very marked individual variation. A striking in- 

 stance occurred with magnesium chlorid, the average toxic limit of 

 which is 0.015 normal. In a solution one-third as concentrated (0.005 

 normal) 2 seedlings out of 20 could not survive. The limit of con- 

 centration for this variety in sodium chlorid is 0.0(')5 normal, but the 

 rootlets of one seedling could not survive in 0.015. Similar to this 

 are the results with sodium sulphate, the toxic limit being 0.05, but 

 the root tips of two individuals did not survive in 0.035 normal 

 solution. 



Padui. — No variation of any importance. 



Afaraouaiii — The rootlets of two seedlings of the Maraouani vari- 

 ety Avere killed in 0.005 normal magnesium sulphate, while ?> out of 20 

 iudividuals survived in 0.015. The average toxic limit for this salt 

 is 0.0075 of a normal solution. 



Knhanl-a. — No important variations. 



NEUTRALIZING EFFECT OF THE SALTS EMPLOYED UPON OTHER 



TOXIC SUBSTANCES. 



Because of a discovery which was made when these experiments 

 were almost completed it is necessary, to add a few remarks upon the 

 neutralizing effect upon other toxic substances of the salts of sodium 

 and magnesium. During the whole course of the experiments the 

 writer was unable to get seedlings to grow or even to live for 

 twenty-four hours in the distilled water used. This seemed unac- 

 countable, as it quite disagreed with the results of other experi- 

 menters. Coupin found the roots of wheat seedlings to thrive 

 well in perfectly distilled water, and Deherain and Demonssy « 

 showed absolutely pure water to be perfectly harmless to root 

 growth. Numerous experiments have been made to determine this 

 point, with more or less varying results. Certain experimenters 

 have held that distilled Avater was not conducive to good growth. 



" Sin- lii Germination dans I'Eau DistillO, Coiupt. Rend., Paris, 132 : 523 

 (1901). 



