IQ20] 



COULTER— A LEU RONE COLOR 417 



tion of ear 639. It is a very striking fact that where no mottling 

 is predicted (647, 635, 636, 644, 652) absolutely none appears. 



II. — PPRRcc (C tester) XppRrCc (East) gave 62:0:52 with 

 no mottling. Half the purple grains should have had the PpRRCc 

 formula, the other half PpRrCc; the white grains, half PpRRcc, 

 half PpRrcc. From the latter, two ears were selfed, both giving 

 0:0:300. 



A cross was made between an individual resulting from one of 

 the colorless grains as female parent, and ppRrCc as male parent. 

 Since the former could be either PpRRcc or PpRrcc, we must 

 consider both possibilities: (1) PpRRcc XppRrCc would give 1:1:2 

 and no mottling (1:0); (2) PpRrccXppRrCc would give 3:3:10 

 and a mottling ratio of 2:1. The actual ratios were 48 : 28 : 78 and 

 76:0, satisfying 1. 



Two crosses were made between individuals resulting from two 

 of the colorless grains as male parents, and PPRrCc as female 

 parent. The two possibilities are: (1) PPRrCc X PpRRcc would 

 give 1:0:1 and 1:1; (2) PPRrCc X PpRrcc would give 3:0:5 and 

 2:1. One of the resulting ears actually gave 115:0:134 and 78:37. 

 The color ratio might be either 1:0:1 or 3:0:5, but the mottling 

 ratio decides the case in favor of 1. The other ear gave 242 :o: 278 

 and 126 : 116. There might be a slight doubt about the color ratio, 

 but the mottling ratio decides in favor of 2. 



Two other crosses in which 2 : 1 mottling ratios were predicted 

 gave 73:38 and 162:65 respectively. We may conclude that this 

 family also fulfils the predictions fairly well. It is interesting that 

 cases in which the color ratio may be a matter of some doubt may 

 sometimes be decided by reference to the mottling ratio. 



III. — This family resulted from a cross reciprocal to the last, 

 or ppRrCc (East) X PPRRcc (C tester). This gave an ear con- 

 taining only 13 grains, so that the ratios are without significance. 

 The same possible genotypes are confronted as under II. One of 

 the colorless grains inbred gave, of course, 0:0:300. A single 

 individual, produced from one of the purple grains, was used as 

 male parent three times, once on its own silks and twice on PPRrCc. 

 If this individual had been PpRRCc, selfing should have given 

 9:3:4 and no mottling, while the cross indicated should have 



