VARIETIES SELECTED. 1 1 



LupiiiiuH alhu.s. Although the order of toxicity of the various saUs 

 leninined the same in the three series of experinieuts, quite diill^'ereiit 

 limits of endurance Avere obtained, those in the first series made l)v 

 the Avriter being nuich higher than those obtained hy Kearney and 

 Cameron and by the writer in his second series. The idea Avas at 

 once suggested by these results that while possibly the second lot of 

 seed may have dilfered only in bein.g younger or otherwise more 

 vigorous it was also possible that different varieties or even merely 

 straius from different sources of the same species might differ con- 

 siderably in their power to resist toxic salt solutions. It Avas there- 

 fore -Avitli a vieAv of determining Avhether or not this Avas true that 

 the series of experiments Avhich forms the subject of this ]-)a]i(>r Avas 

 undertaken Avith difi'ereut varieties of AA'heat. 



Attention should be directed at the outset to an important condi- 

 tion under which this AAork Avas carried on. Most of the Avork of 

 this kind has been conducted Avith comparatively few seedlings. But 

 indi\idual variation in resistance is Avell knoAvn to be exceedinsrlA' 

 great, and enough seedlings must be tested to eliminate all such differ- 

 ences. The a\'erage of the resistances of a large luimber of seedlings 

 nnist be ascertained. The Avriter has in every case used from 50 to 

 100 seedlings, and more in some cases, the number tested being con- 

 sidered sufficiently large to eliminate indiAndual variation and give 

 fairly consistent results. The total number of seeds cxi^erimented 

 Avith aggregated nearly 5,000. 



The Avork, the results of Avhicli are shoAvn in this paper, Avas taken 

 up at the suggestion of ]Mr. Thomas H. Kearney^ Physiologist, of the 

 Laboratory of Plant Breeding of the Department of Agriculture. 



SALTS USED. 



It Avas decided to employ the same salts used by Kearney aud 

 Cameron in their Avork Avith Lupin.us alhus, i. e., sodium chlorid 

 (XaCl), sodium sulphate (Xa.SOj), sodium carbonate (Na.COo), 

 sodium bicarbonate (NallCOa), magnesium sulphate (MgSO^), and 

 magnesium chlorid (jNIgCL). A basis for direct conq^arison is thus 

 ol)tained. It Avas thought best to use these salts, also, because of their 

 counnou occurrence in saline soils, and their tendency, in a greater 

 or less degree, to inhibit A'egetable groAvth. 



VARIETIES SELECTED. 



The selection of the A'arieties of Avheat to l)e used in this Avork has 

 not beeri an easy matter, there being a number of details to consider 

 in making the choice. To prove Avhether there is a difference in the 

 ])<)\ver of different varieties of the same species to resist the action 

 of toxic salt solutions it Avas decided to use A'arieties representing A'ery 



