418 BOTANICAL GAZETTE [may 



given 3:0:1 and 1:1. If it had been PpRrCc, selling should have 

 given 27:9:28 and 2:1, the cross 9:0:7 and 2:1. Actually selling 

 gave 207:63:90 and 270:0, clearly indicating the former. In 

 the two cases of the cross indicated, the actual color ratios were 

 411:0:127 and 360:0:129. These are 3:0:1 ratios, and satisfy, 

 as before, the formula of PpRRCc for the male parent. The 

 mottling ratios in these cases, however, were respectively 278:133 

 and 235:125. Obviously, where it was felt that 1:1 mottling 

 ratios could be predicted with some certainty, the actual ratios 

 obtained were strikingly close to 2:1. The writer fully realizes 

 the care which must be exercised in classifying mottled grains. 

 These particular ears were not only shelled (as usual), but were 

 counted twice, using the same standards as proved satisfactory 

 elsewhere. One is forced to conclude that these additional data 

 represent an exceptional behavior, sufficiently decisive to be of some 

 real significance. 



IV. — pprrCC (East) XPPRRcc (C tester) gave unusual data. 

 It is unnecessary to give all of them ; sufficient at present are the 

 mottling ratios obtained. Four ears resulted in which mottling 

 was to be expected in a 2 : 1 ratio. The actual ratios obtained were 

 155:0, 30:8, 151:3, and 177:3. Obviously the usual mottling 

 situation is absent. The question arises whether the few so-called 

 mottled grains were truly such. It is probable that they were not, 

 since there have been known to occur various types of anomalous 

 grains which may readily be confused with true mottling. Had 

 these grains occurred on ears known to contain true mottling, they 

 would have been included in that class. I feel justified, therefore, 

 in the tentative conclusions that (1) the P, R, and C factors of 

 East and Emerson are probably identical; (2) mottling is due to 

 a heritable factor (or factors) which is present in Emerson's C 

 tester and absent in the material of East, and that this factor prob- 

 ably behaves immediately as a dominant, no matter with which 

 parent it enters the cross. No attempt is made at present to explain 

 the 2 : 1 mottling ratios which appeared in two cases of family III 

 instead of the expected 1:1. As for family IV, this situation may 

 be explained by assuming that not all of the C tester material was 

 homozygous for the presence of the mottling factor. 



