172 LOCK : STUDIES IN PLANT BREEDING 



process equal numbers of flowers yielded white endosperms 

 (recessive) and yellow endosperms — evidently heterozygous 

 Mnce the male parent was white. The pollen of the hetero- 

 zygote was tested in the same way and with the same result. 



Prof. Pearson asks, Where is the other homozygote ? In 

 the last generation (as described in Nature) heterozygote 

 plants were mutually pollinated and yielded a proportion of 

 three yellow grains to one white. One out of every three 

 yellow grains in this generation represents the other (yellow) 

 homozygote. 



A further series of cases, in which the presence and absence 

 of a colour were concerned, require particular notice owing 

 to the fact that the cross between heterozygote and white 

 often yielded a sensible excess of whites over the expected 50 

 per cent. These were all found in crosses between parents 

 one of which showed the blue or purple pigment in the aleurone 

 layer ; and the phenomenon was seen alike in crosses between 

 definite strains and between mongrel plants. In the former 

 case the reason of the phenomenon was at once apparent, 

 since heterozygote grains arising from the cross white x blue 

 might be either blue or white in colour, so that both kinds of 

 grains were to be seen on the same cob, when the latter arose 

 from the fertilization of a white strain with pollen from a 

 blue (black). 



At this point it is necessary to recall the methods of polli- 

 nation employed throughout these experiments. In the one 

 set of cases heterozygote plants were grown together in groups 

 and allowed to intermingle their pollen, the pollen of other 

 plants being excluded by distance. In the second set of cases 

 1 which include the great majority, heterozygote plants deprived 

 of their male inflorescences were exposed to the pollen falling 

 from many plants of one particular strain (usually a recessive). 

 Tims in no case can the ezaot individual parentage of the 

 rains <»n the plant under consideration be arrived at. If this 

 had I" mi possible there is little doubt that the apparently 

 omplicsted phenomena eefl would receive their propei 



