RESULTS WITH PURE SOLUTIONS. 



11 



The Edra variety is slightly less resistant than the preceding variety. 

 It will be noticed that this variety, as well as the Dwarf Milo, 

 can endure a greater concentration of sodium bicarbonate than the 

 Early Amber, although the latter is the variety that is most resistant 

 to most of the salts. Of magnesium chlorid a concentration of 0.00625 

 normal is critical for the Early Amber variety, which is more than 

 twice the concentration that is critical for the Edra variety, and five 

 times that which is critical for the Dagdi Juar variety. The last is 

 decidedly the most sensitive of the four varieties. The Edra is some- 

 what more resistant than the Dwarf Milo to sodium chlorid, but the 

 variation in resistance to this salt, as well as to sodium sulphate, is 

 very slight with all the varieties. 



In the case of Andropogon sorghum as in that of Triticum the great- 

 est difference in resistance among the different varieties is shown in 

 the presence of the more harmful salts. To the less harmful salts — for 

 example, the chlorid and sulphate of sodium — there is less variation in 

 resistance. 



RESULTS WITH OATS ( A VENA SATIVA). 

 Table IV. — Limits of endurance of oat seedlings of salts of magnesium and sodium. 



Salts used. 



Magnesium sulphate 

 Magnesium chlorid . 

 Sodium carbonate . . 

 Sodium bicarbonate 



Sodium sulphate 



Sodium chlorid 



Critical concentrations. 



Red Algerian. 



Culbertson. 



0. 001875 normal 



0. 000625 normal 



. 001875 normal 



.0005 normal 



.00625 normal 



. 0075 normal 



. 0075 normal 



. 009 normal 



. 0175 normal 



.015 normal 



. 02 normal 



. 015 normal 



The Red Algerian variety of Avena sativa can endure a concentra- 

 tion of magnesium sulphate three times as great as that which is 

 critical for the Culbertson variety. There is about the same amount 

 of difference in resistance to magnesium chlorid, the Red Algerian 

 being again the more resistant. The Algerian variety is more resist- 

 ant than the Culbertson to every salt except two (sodium carbonate 

 and bicarbonate), and in these cases the difference is but slight. It is 

 interesting to note that the former variet} r , which came originally 

 from Algeria, where it is said to be grown successfully in soils con- 

 taining a considerable amount of harmful salts, shows also a greater 

 power of resistance to salts in pure solutions. 



RESULTS WITH SUGAR BEETS (BETA VULGARIS). 



The * w Original Klemwanzleben r strain of the sugar beet was 

 selected for use in these experiments. 



113 



