B. r. I.— 159. 



V. p. r. T. — in4. 



THE VARIABILITY OF WHEAT VARIETIES IN 

 RESISTANCE TO TOXIC SALTS. 



INTRODUCTION. 



It has been shown quite conchisively in recent years that different 

 species and genera differ very much in their ability to resist the influ- 

 ence of toxic salt solutions. Numerous investigations of the action 

 of acids and salts upon plants have been made, especially during the 

 last four or five years. In\'estigations of this nature are not only of 

 great scientific interest, l)ut promise in some cases to be of consider- 

 able practical importance. One phase of this subject which is espe- 

 cially interesting from this latter point of view is that of the relation 

 of plants, particularly cultivated plants, to the components of the 

 saline or alkaline soils that are so common in the arid part of the 

 United States and of many other parts of the world. 



A preliminary investigation of this phase of the subject was made 

 by Messrs. Kearney and Cameron," Avho showed by a large number of 

 experiments on LupiuK^ albus and Medtcago satioa that the death 

 limit of the root tips was very different for different salts. For 

 instance, the limit for Liipinus alhiis in sodium chlorid was found to 

 V)e 0.02 of a normal solution, and in magnesium sulphate 0.00125. 

 For Medicago sativa, in mixed solutions containing an excess of two 

 calcium salts, the limit was 0.35 in magnesium sulphate and 0.20 in 

 sodium chloi'id.'' 



Much work has been done in comparing different botanical species 

 as to their resistance to the effect of salt solutions,'' but the compara- 



a Report No. 71, U. S. Dept. of Agriculture (1902). 



^ Messrs. KalilenlKH-g and True, who have done considoraI)le work along this 

 lino, particailarly with salts and acids, give some very interesting results. They 

 loiuid (On the Toxic Action of Dissolved Salts and Their Electrolytic Dissocia- 

 tion. Bot. Gaz., 22:81, 180(5) that Liiphius alhus would just survive in -^^1^^^ 

 gram mol. per liter of copper salts. They found the same limits with ferrous 

 suli)hate (FeS04). nickel sulphate (NiSOJ, and cohalt sulphate (CoSOJ, but 

 for mercuric chlorid (HgCU) y^loo, '"^^l mercuric cyanid (HgCn„) only 



'■The experiments of Heald (On the Toxic Effect of Dilute Solutions of Acids 

 and Salts upon Plants, Bot. (Jaz., 22: 12."). 1S'.)(>), and later those of Moore and 

 Kellerman, are among the most interesting in this connection. 



Ileald, in a series of experiments resembling those of Kahlenberg and True, 

 obtained some valuable results with CuviirhUa pcpo, Zca nicu/s; and Pisuin •sail- 

 30012— No. 7U— 05 m 2 9 



