30 



WHEAT RESISTANCE TO TOXIC SALTS. 



will serve for iiiakiiio- comparisons, hut not J'or drawing conclusions 

 as to the behavior of plants in general. 



RESULTS WITH SODIU^M SULPHATE. 



The comparative effect of pure solutions of sodium sul2)hate upon 

 the difi'erent varieties is shown in the table which follows : 



Name of wheat variety. 



Zimmerman .. 



Kharkof 



Pacini - 



Knbanka . 



Tnrkey 



Mai-aouani 



Budapest 



Preston 



Chul 



Average for all vai'ieties 



Maxiranm limit of 

 endurance. 



Parts per 

 1(X),(KK) of 

 solution. 



Fractional 

 parts of a 

 normal so- 

 lution. 



353 



m) 



818 



'.m 



300 

 336 

 2tj.j 

 242 

 283 



305 



fl. 0.5 

 .0425 

 .045 

 .05 

 .0425 

 .0475 

 .0375 

 .035 

 .04 



.0433 



In sodium suliihate, as in sodium bicarbonate, the toxic limits for 

 the dilferent varieties show less variation than in the case of other 

 salts used. The least resistant to this comparatively harmless salt, 

 as to most of the others used in these experiments, is the Preston 

 wheat. This variety has been grown for a number of years in a 

 semihumid region where alkali soils do not occur. In view of these 

 facts one would expect this variety to be somewhat less resistant 

 to these salts. Since there is no excess of soluble salts in the soils 

 of this region, Preston has had no opportunity to develop salt resist- 

 ance. The varieties most resistant to sodium sulphate are Zimmer- 

 man and Kubanka, both surviving as well in a 0.05 normal solution 

 as Preston in 0.035. As to the origin of these varieties, also, it is just 

 what would be exjjected from their resistance to salts. Both sorts 

 came from arid or semiarid regions, Avhere saline soils are abundant. 

 Kubanka is grown in regions containing numerous salt marshes and 

 lakes, and that it should have acquired ability to resist salts in the 

 soil is only natural. Zimmerman likewise was obtained from a 

 region having soils of more or less saline character, and to this 

 is probably due its power of resistance in salt solutions. It is not 

 unlikely that the soils from the regions from which the remaining 

 varieties were obtained contain a less amount of sodium sulphate 



