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THE AMEBIC AN NATURALIST [Vol. XLVII 



tions in the potato that are known to mendelize in sexual repro- 

 duction, but has regarded these occurrences as a segregation of 

 characters in somatic cell divisions (of a heterozygous plant?) 

 rather than as a change in genetic factors, which alone can be 

 regarded as a true mutation. 



The interpretation that I have given to the results of a study 

 of the inheritance of a recurring somatic variation in maize have 

 some interest in this connection.* The results in brief are 

 these: (1) The more red there is in the pericarp of the seeds 

 of variegated-eared maize ("calico" corn), the more likely is 

 the progeny of these seeds to have self-red ears and the corre- 

 spondingly less likely to have variegated ears. (2) Red ears 

 thus produced behave like F 1 red ears produced by crossing 

 self-red races with variegated races or self-red races with white 

 races, depending upon whether the variegated parent ear was 

 homozygous or heterozygous and upon whether it was selfed or 

 cross-pollinated. (3) Red ears that behave exactly like crosses 

 between pure reds and pure whites occasionally arise from the 

 seeds of white races crossed by pollen from variegated races. 



My interpretation of these results postulates the presence of 

 a genetic factor for self-color, S, in occasional gametes instead 

 of the ordinary variegation factor, V. The presence of S in 

 female gametes is apparently due to a change of V to S in 

 somatic cells from which these gametes arise and this change in 

 genetic factors apparently manifests itself in the development 

 of red pigment in such pericarp cells as are directly descended 

 from the original modified cell. The larger the mass of modified 

 cells the more red appears in the pericarp and the more likely 

 are the female gametes to carry the S factor. But since red 

 never develops in the pericarp until the seeds are nearly mature, 

 it happens that the somatic variation does not become visible 

 until weeks after the gametes are formed and until still longer 

 after the change in factors occurs. It is reasonable to suppose 

 that the presence of the S factor in the male gametes is due to the 

 same sort of change in the somatic cells from which they arise as 

 that responsible for the presence of 8 in the female gametes. This 

 somatic variation, however, never becomes visible because the 

 staminate inflorescence dies very soon after the pollen is shed. 

 It is quite possible indeed that such a somatic change would 

 never become apparent even if the tassel did not die too early, 

 for a color limited principally to the cob and to the pericarp of 

 the seeds could scarcely be expected to appear in the tassel. 



It seems possible that the production of self-colored plants 



