31 



shown, as red dent corn, where the color is in the pericurp, does not 

 appear to cause xenia. (See p. 2<U.) 



In the writer's experiments it Avas found that the phnn))eous or 

 bhiish-black coh)r of the aleurone layer of the endosperm in the Cuzco 

 and l^lack Mexican races was apparcnth' shown in almost all cases as 

 xenia when these races were used as the pollen parents in crossing 

 with white or yellow races of dent, flint, or sweet corn. Where, how- 

 ever, the race having the dark-colored aleurone layer is used as the 

 female parent and is crossed with pollen of yellow and white races it 

 would seem that xenia is not so lialile to show, but the writer's experi- 

 ments have not been sufficiently extended to demonstrate this conchi- 

 siveh'. According to one of Correns's^ propositions it is impossible 

 for xenia to show as change of color when a race with a y(^llow endo- 

 sperm and blue violet aleurone Vdyev is crossed with a race in which 

 the endosperm and aleurone layer are white or colorless. If the writer's 

 hj^Dothesis in regard to the formation of mosaic or variegated kernels 

 by xenia, discussed in detail later on, is true, it would seem probable 

 that races with dark-colored aleurone layers could, at least in some 

 cases, be influenced In- crossing with races with colorless aleurone 

 layers. This question, however, can not be settled without further 

 experiments. 



The chemical composition of the endosperm has been found to be 

 greath" changed as a result of xenia. Sweet corn crossed with pollen 

 of dent or flint races produces smooth kernels with starchy endosperm 

 like the male parent, this feature being very noticeable. In this case 

 the sweet corn, if a dark-colored race like the Black Mexican, may 

 produce the smooth, starch}^ kernels of the male parent, but retain its 

 original color unchanged, as in the case of Black Mexican X Gihnan 

 Flint (see p. 291). If, however, the race of sweet corn used is hyaline, 

 the color as well as the chemical composition may be changed as in the 

 case of Stoweirs Evergreen X 3^ellow dent (experiments 13a and 13b, 

 p. 23) or white dent (PI. II, fig. 4). Dent races, however, in which the 

 endosperm is starchy, do not seem to show xenia by changing to the 

 sweet corn type of endosperm (experiments 11a, 16a, 31a, and 31b, etc.). 



Flint races crossed with sweet corn may show xenia in the wrinkled 

 t3^pe of sweet-corn endosperm produced as in the case cited of Gilman 

 Flint X Stowell's Evergreen (p. 21); also PI. IV, fig. 3). In this case 

 the kernels, while showing the wrinkled character of the male parent, 

 retained the yellow color of the mother parent. This instance of the 

 effect of pollen from a race with sugary endosperm on a race with 

 starchy endosperm in producing wrinkled kernels apparently with 

 sugary endosperms forms an exception to Correns's proposition 14, that 

 xenia may result in that " a more complicated chemical compound 



^Correii!:?, 1. c, Propositions 1, 2, and 14. 



