SUMMARY. 45 



behaA'ior Avheii brought into relation with saline or alkaline soils. 

 But the species itself may include a great number of ditt'erent varie- 

 ties or races, as in the case of wheat. It is not enough to know that 

 wheat in general is better adapted to a certain region because of soil or 

 climatic conditions than is Indian corn or cotton, but in addition it is 

 necessary to know Avhioh of the many varieties of wheat is best suited 

 to that region. wSnch knowledge might save many years of constant 

 selection with a view to acclimatization. 



Soils are often known to contain sodinm chlorid or magnesium 

 sulphate or some other salt in such quantity as to be fatal to some 

 varieties, while permitting others to flourish. Now, it has been pos- 

 sible by these experiments to determine that some varieties of wheat 

 are much more resistant to a particular salt than others, and they are 

 the ones which would be expected a priori to thrive best in a region 

 where that salt predominates, other conditions being equal. By some 

 of the experiments it was found that some varieties would thrive 

 equally well in three times the concentration of sodium carbonate as 

 others. A simple deduction from such results would be that for a 

 region containing large quantities of " black alkali '' the variety 

 shown to have the greatest resisting power should be selected. 



A knowedge of the limits of individual variation within each 

 variety is likewise very essential. Often the most resistant varieties 

 are not always the most desirable in other respects and a sort which 

 is less resistant would be preferable. In case such a sort has a great 

 individual variation in resistance to salts it should be compara- 

 tively easy to introduce it by gradual selection of the most resistant 

 individuals, though a little more time would naturally be required 

 than in introducing a variety that is already more resistant, as a 

 smaller percentage of the plants would survive to furnish seed for the 

 next crop. 



It is believed, therefore, that the results of these exiieriments afford 

 additional j)roof that the adaptation of useful cultivated plants to 

 saline or alkaline soil conditions is one of the most promising of 

 plant-breeding problems. 



SUMMARY. 



(1) The salts with which the experiments were made are injurious 

 to wheat seedlings in the following order: ^Slagnesium sulphate, 

 magnesium chlorid, sodium carl)onate, sodium bicarbonate, sodium 

 sulphate, and sodium chlorid. This is asserted as true only of wheat, 

 and a quite (liferent order might possibly be established for other 

 plants. 



(•2) The results obtained from a few individual seedlings are inac- 

 curate and unreliable. A large number nuist be tested in order that 



