154 



T.OPK : STUDIES TN PLANT BREEDING 



The figure clearly shows the discontinuity between the hete- 

 rozygotes in which dominance has become regular and those in 

 which this is not the case. It also indicates on the whole a 

 wide distinction between the offspring of white and of blue 

 heterozygotes. According to the present interpretation of the 

 facts, the offspring of two kinds of individual grains are mingled 

 in the group which lies just above 50 per cent., namely, of 

 homozygotes in whose offspring dominance of blue sometimes 

 fails, and of heterozygotes among whose offspring dominance 

 is tegular or nearly so. The distinction made between these 

 two groups is admittedly more or less artificial. 



F4, 



h'.rpt. 67. — In the next generation (F4) the offspring of a 

 plant of the above series (Expt. 66) which produced ex- 

 clusively blue grains was examined. The plants in this case 

 were grown in an isolated situation and allowed to undergo 

 mutual pollination. This process unfortunately obscures the 

 natural differences in the proportion of blue and white grains 

 shown by individual plants, nevertheless it seems clear from 

 a comparison with the preceding evidence that there was 

 regular dominance of blue in the case of a majority of plants, 

 whilst in the remainder blue was again recessive in the case of 

 a certain proportion of the germ cells. 



No. 



I 

 2 



3 



1 



6 



7 



B 

 10 



11 



White. 



190 

 216 



175 

 249 

 252 

 21 I 

 207 

 169 

 2] I 



Table 43. 



Blue. 



245 

 344 

 283 

 436 

 439 

 ::7s 

 383 

 328 

 H9 

 is 1 

 40] 



Total. 



135 

 560 



158 

 686 

 691 



590 

 197 

 630 

 728 



r>no 



Per cent. 

 White. 



43-7 

 386 

 38-2 

 37 4 

 36-6 



36 • 8 

 35 1 



.m- 11 



33 • 5 

 33 4 



33 • 1 



