i 9 2o] COULTER— A LEU RONE COLOR 419 



The R tester material was similarly crossed with East's 

 material. The color ratios obtained in five small families fully 

 satisfied the predictions. The mottling ratios obtained, however, 

 were quite different from those before, and may be summarized 

 as follows: (1) ten ears gave 100 per cent colorless aleurone, and, 

 of course, no mottling; (2) there were nine ears in which the R 

 factor, wherever present, had come in with the female parent; in 

 these, therefore, no mottling was to be expected; these gave a total 

 of 889 self-colored grains to 1 mottled; (3) c^ses in which a 2:1 

 mottling ratio might have been expected may be taken up separately 

 for the different families. Family I, produced by PpRrCc (East) 

 XPPrrCC (C tester), gave three such ears, with a total of 467 self- 

 colored: 5 mottled grains (1.06 per cent mottling; extremes 

 1.85 and 0.00 per cent). Family II gave four such ears with a 

 total of 333:30 (8 . 26 per cent; extremes 12.12 and 5.52 per cent). 

 Family III gave one such ear with 58 :o. Family IV gave nine such 

 ears with a total of 1840:23 (1.23 per cent; extremes 2.22 and 

 0.00 per cent, one case). Family V gave three such ears with 

 638:51, or 7.40 per cent mottling; but that is not all. One of 

 these ears gave 263 : 10. The other two were identical with respect 

 to both their parents, both growing on the same plant. One of 

 them gave 237:41, the other 138:0. 



One hesitates to draw any general conclusion from these data. 

 Certainly R tester does not contain that essential factor for mottling 

 which was present in C tester. In the event that Emerson's C 

 tester and R tester were extracted fairly recently from the same 

 parent stock, the present situation might suggest that this unknown 

 mottling factor was an attribute of Emerson's R factor itself, or 

 at least closely linked. This, however, would involve some 

 awkward, although not impossible, assumptions to explain the 

 behavior of mottling in those families produced by crosses of C tester 

 with East's material; for, of course, the latter did not contain the 

 mottling factor. The situation would be somewhat simplified if 

 it were sweepingly assumed that the mottling which appeared in 

 these R tester families (just described) was not true mottling at all, 

 but just an imitation. True enough, mottling is at times fairly well 

 imitated, but these particular imitations were so like the genuine 



