The Endosperm in Inheritance 153 



ditions. The required conditions were peculiar and interesting. 

 If the R factor enters the cross with the male parent only, a mottled 

 aleurone results; if the R factor enters with the female parent only 

 or with both parents, solid red is the result. Thus there is a pheno- 

 typic distinction between grains having but one dose of the R 

 factor (male parent only) and those having two (female parent 

 only) or three doses (both parents). Furthermore, this phenome- 

 non will not appear in all races of corn, but only in those which 

 contain a dominant factor for mottling {S, for "spotted" aleurone, 

 as Kempton calls it). 



Webber's explanations, (i) and (2), however, might still 

 apply to the anomalous grains of the mosaic type (6). Proposi- 

 tion (i), that the second male nucleus fails to fuse, and acts inde- 

 pendently in endosperm formation, was proved to be impossible 

 by some of the experiments of East (2). Factors R and C must 

 be present simultaneously for the production of red aleurone. A 

 cross between two colorless types, CCrr and ccRR, therefore, 

 should produce only red grains. Even here, however, aberrant 

 grains sometimes appear, part of the grain being red and the rest 

 colorless. Failure of the second male nucleus to fuse with the 

 female polar nucleus in such a case would result in a grain which 

 was entirely colorless, a thing which never occurred. It is only 

 by fusion of male and female nuclei that any part of the 

 aleurone can be red. The experiments on this point were suf- 

 ficiently extensive to demonstrate that the second male nucleus 

 never fails to affect a fusion with at least one of the female 

 nuclei. 



There yet remained, however, Webber's possibility (2), 

 fusion of the second male nucleus with only one of the female 

 polars, the other female polar acting independently. This last 

 possibility was disproved by Emerson' (3) in the following inter- 

 esting manner. A colorless, sugar>' type, CCrrsusu, was used as 

 female parent in a cross with a colorless, starchy type, ccRR^uSu. 

 The resulting grains were red, starchy, save for a few aberrant 

 grains which were red in part and colorless in part, but starchy 

 throughout. Webber's proposition (2) fails here, since fusion 

 of the second male nucleus with only one of the polars would pro- 

 duce grains which were red, starchy in part (from male nucleus 



