TEE AMERICAN NATURALIST [Vol.LVI 



self-colored ears. Self-colored seeds thus produced have, 

 so far as tested, proved to be heterozygous for self color, 

 behaving in later generations exactly as if produced by 

 crosses of self-colored with variegated or with white 

 races. 



Certain cultures of self-colored maize produce a few 

 variegated seeds. Such seeds have been observed only 

 on ears that are heterozygous from previous crosses with 

 variegated strains, 8 V, or with white strains, ^S' TF, never 

 from ears that are homozygous for self color, *S' S. From 

 such variegated seeds, new variegated races have been 

 produced. 



These facts are regarded as indicating (1) that the oc- 

 currence of self-colored or partly self-colored seeds on va- 

 riegated ears is due to somatic mutations of the recessive 

 variegation gene to the dominant self -color allelomorph; 

 (2) that only one of the two variegation genes of homo- 

 zygous variegated maize mutates at a given time; (3) 

 that it is always the variegation gene, never the w^hite one, 

 of heterozygous material that mutates; (4) that the oc- 

 currence of variegated seeds on otherwise self-colored 

 ears is due to reverse mutations from the dominant self- 

 color gene to the recessive variegation allelomorph ; and 

 (5) that only one of the duplex genes of self -color strains 

 so mutates at any one time, for otherwise there would re- 

 main no dominant self -color gene to prevent the expres- 

 sion of the mutation as variegated seeds in homozygous 

 self-colored material. 



Another type of somatic variation, quite distinct from 

 the self -color mutations discussed above and often termed 

 dark-crown variation, also occurs frequently in varie- 

 gated maize pericarp (Emerson, 1917). It is quite as 

 striking in appearance as the self -color mutation, but is 

 not inherited, the progenies of the aberrant seeds being 

 in no way different from those of the nonnal seeds of the 

 same ears. Microscopic examination of d.-irk-ci-ow n .ind 

 of self-color seeds indicates that in the toniicr ilie e[)i- 

 doi-mis alone is colored while in the latter the epidermis 

 alone remains colorless. The conclusion seems war- 

 ranted, therefore, that the two types of variation are fun- 

 damentally the same, both being true gene mutations, and 



