PREFACE. 



The main object of the accompanyino- paper is to prove that differ- 

 ent varieties of a single species behave differently in the presence 

 of the harmful salts that are present in the so-called alkali soils of 

 the western United States. The work has been done with varieties 

 of wheat on account of the great importance of that crop in the 

 region indicated and because, being grown under a great diversity 

 of conditions as regards climate and soil, wheat varieties would be 

 exjoected to differ much among themselves in their power to with- 

 stand the effect of excessive amounts of salts in the soil, just as they 

 differ widely in their capability of withstanding drought, cold, and 

 parasites. 



The experiments were made with young seedlings, their roots being 

 exposed for periods of twenty-four hours to the action of pure solu- 

 tions of the salts used, the greatest strength of solution in which 

 the root tips could survive being taken as representing the limit of 

 endurance of each variety to each salt. The salts used were the car- 

 l)onate, bicarbonate, sulphate, and ehlorid of sodium, and the sul- 

 phate and ehlorid of magnesium. These are salts that are generally 

 present in the largest quantity in alkali soils. Nine varieties of 

 wheat, both from the Old AVorld and the Xcav, representing widely 

 different climates and soils, were compared. 



It was found that the varieties differed greatly in their ability to 

 withstand the poisonous action of the salts used. This was more 

 strikinfflv broui»"ht out in the case of some salts than of others. To 

 magnesium sulphate, for example, some varieties are three times 

 as resistant as are others. Tables are given in the following paper 

 showino- the limit of concentration of each of the nine varieties foi 

 each of the six salts. It was also clearly demonstrated that the dif- 

 ferent individuals of each variety differ much in resistance, and the 

 limits of the varieties as established are only the means of the limits 

 for all the individuals tested. Analyses of the ash of each lot of seed 

 used were obtained from the Bureau of Chemistry, but no correla- 

 tion could be shown between ash composition and resistance to action 

 of toxic salts. On the other hand, it was clearlv demonstrated that 



