[Chap. XXXVIII HYBRID SEGREGATION 473 



Xenia is the evident result of the influence of the pollen parent on the 

 endosperm of the ovule parent the same season that cross-pollination 

 occurs. Hence, it will occur only in seeds in which an endosperm de- 

 velops from the triple-fusion nucleus. Furthermore, the sperm must con- 

 tain a dominant endosperm factor, and the fusion nucleus the contrasting 

 recessive endosperm factor. 



If seed "C" in Fig. 214 is planted and only self-fertilization occurs, in 

 the mature plant that develops from the embryo there will be two kinds 

 of pollen grains, two kinds of embryo sacs, four kinds of triple-fusion 

 nuclei, and an ear of corn on which 3/4 of the grains will be blue and 

 1/4 will be white, as shown in Figs. 216 and 217. 



The fact that the ovule in a grain of corn is enclosed in the closelv 

 adhering ovularv is not shown in the diagram. Some of the colors in 

 grains of corn are due to pigments in the grain coats. Xenia, however, 

 is strictly an endosperm phenomenon. 



We have described here a simple example of hybrid endosperms. 

 Other examples, some of which are complicated because of partial domi- 

 nance, linkage, or multiple factors, have been analyzed and explained 

 in the literature. 



GENERAL REFERENCES 



Altenburg, Edward. How We Inherit. Henry Holt & Company, Inc. 1928. 

 Castle, W. E. Genetics and Eugenics. Harvard Univ. Press. 1922. Translation 



of Mendel's paper in appendix, 

 litis, Hugo. Life of Mendel. W. W. Norton & Company, Inc. New York. 1932. 

 Weatherwax, Paul. The Story of the Maize Plant. Univ. of Chicago Press. 1923. 

 Zirkle, Conway. The Beginnings of Plant Htjbridization. Univ. of Pennsylvania 



Press. 1935. 



SELECTED REFERENCES 



Rabcock, E. R. Recent progress in plant breeding. Sci. Monthly. 40:313-322. 



1935. 

 Harbou, D. J. Gregor Johann Mendel. Sci. Monthly. 49:393-400. 1939. 

 Waller, A. E. Xenia and otlier influences following fertilization. Ohio. Jour. 



Sci. 17:273-284. 1917. 



