MATERNAL INHERITANCE 229 



does not differ in any essential respect from ordinary 

 Mendelian heredity. 



A peculiar case that in some respects and in certain 

 combinations appears to be maternal inheritance, is 

 shown in the character of the seed of com {Zea mais). 



The endosperm of maize is produced, as in some other 

 plants, at the time of fertilization — ^one pollen nucleus 

 unites with the Qgg to form the embryo, another poUen 

 nucleus unites with two nuclei in the embryo-sac to pro- 

 duce the endosperm whose cells, therefore, aj-e triploid. 

 Floury corns have an endosperm, that is almost wholly 

 made up of cells containing "soft" starch, while flint corns 

 have only a small amount of soft starch in the centre of 

 the seed which is surrounded by a large amount of hard 

 "corneous" starch. Hayes and East have shown that if 

 a floury com be used as the mother and a flint corn as the 

 father, the seeds are floury like those of the pure race of 

 floury corn. If a flint corn be used as the mother and a 

 floury com as the fathfer, the seeds are flinty. In both 

 cases there is apparently maternal inheritance, at least 

 as far as the endosperm is involved, which is not, how- 

 ever, a part of the embryo proper. If the seeds from races 

 of the foregoing crosses are sown and the plants allowed 

 to self -fertilize, the following results are obtained: The 

 jPi derived from floury 9 by flint $ produces both floury 

 and flint in F2 in the ratio of 1 : 1. The F^ flinty reciprocal 

 cross gives exactly the same result. The explanation of 

 the Fi and F^ results is as follows : If the factor for flinty 

 be F, and that for floury be f, then in the first cross the 

 endosperm is jfF and in the reciprocal cross FFf. Since 

 fF is floury and FFf flinty it follows that two doses of 

 floury dominate over one dose of flinty, and conversely 

 two doses of flinty dominate over one dose of floury. 



The Fj embryo, however, in each of the crosses has 

 only one F and one / factor {Ff) . Its gametes are F and 

 /, and so are its endosperm nuclei which, as shown by 

 Weatherwax have the same reduced formula as the ovules 



