Selection upon Mendel/an Character 187 



The behavior of red pericarp color is throughout this experiment 

 consistently that of a Mendelian dominant, the only peculiarity 

 of the case being that the dominant character is manifested only 

 in maternal structures, not in paternal ones or in those of the 

 embryo itself. 



Again, if white-seeded maize is pollinated with pollen from a 

 red-seeded variety, the color of the seed is not affected, though 

 the contained embryos are heterozygous, R(W). The seed ac- 

 cordingly is white, but plants raised from it bear red ears. And 

 if another generation of plants is raised from such red seed, these 

 prove to be of three sorts, as in the reciprocal cross, viz: iRR, 

 2RW, and iWW. The RR and RW plants bear red ears, the 

 WW plants bear white cars, though all the plants alike were 

 raised from red seed. 



It follows that a red seed-coat may cover an embryo of any one 

 of these sorts, RR, RW, or WW, but a white seed-coat may cover 

 only two of these three sorts of embryos, viz: RW or W^V. For 

 the white seed must have received a maternal contribution of 

 white, though the paternal contribution may have been either R 

 or W. 



If accordingly one selects seed by color alone from a mixed race 

 of red and white, neither the red seed nor the white seed will breed 

 true, either at the outset or after repeated selections. This fact, 

 however, is not inconsistent with a strict Mendelian behavior of 

 pericarp color in heredity. Ii in the supposed case selection is 

 carried out on a considerable scale, we can predict with consider- 

 able accuracy what the proportion of red to white ears will be 

 following each selection. 



Reciprocal crosses between red seeded and white seeded vari- 

 ties yield the same results so far as seed-color in the hybrid plants 

 and in their offspring is concerned. The Fj hybrid plants bear 

 only red ears. Accordingly it is impossible in this generation to 

 make any selection for seed-color. Some of the F2 plants bear 

 red ears, some white ears. Here then selection may begin. If 

 one saves only white ears for seed in this and subsequentgenera- 

 tions, the proportion of white to red ears in each successive crop 

 should be approximately as shown in Table i; if on the other 

 hand one saves only red ears for seed, the proportions should be 

 approximately as shown in Table 2. 



