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THE AMERICAN NATURALIST [Vol. XL VI 



yellow was lighter in color than the homozygous, and hence dis- 

 tinguishable from it. In crosses between yellow and non-yellow 

 endosperm, when the non-yellow endosperm was entirely soft 

 (not corneous), as in the so-called flour corns, xenia appeared in 

 all cases, for reasons just stated. "When the endosperm of the 

 non-yellow parent was entirely corneous, as in the popcorns, xenia 

 usually occurred only when yellow was used as the male parent, 

 though in a few instances it was perceptible when the cross was 

 made the other way. Xenia also occurred when purple or red 

 aleurone was crossed with non-purple, or non-red, when the pur- 

 ple or red was used as the male. The only other case in which 

 xenia was observed was in crosses between white and red (or 

 purple) when the white (male) parent carried an inhibiting 

 factor for purple and red. Sometimes the reciprocal cross shows 

 xenia, since the inhibition of red or purple is not always com- 

 plete. The following law regarding xenia is formulated by the 

 authors: when two races differ in a single visible endosperm 

 character in which dominance is complete, xenia occurs only 

 when the dominant character is the male ; when they differ in a 

 single visible endosperm character in which dominance is in- 

 complete or in two characters both of which are necessary for the 

 development of the visible difference, xenia occurs when either 

 parent is used as the male. 



Correns's conclusion that where xenia occurs the seeds showing 

 it are always hybrid is confirmed. This shows that Mendelian 

 segregation must occur previous to the division of the pollen nu- 

 cleus. The authors found no case in which a seed showing no 

 xenia where it is to be expected proved to be a hybrid ; i. e., the 

 hybrid in which xenia is to be expected always showed xenia 

 , though like Webber and Correns they found seeds showing xenia 

 on only one side. This is interpreted as the result of the inde- 

 pendent development of the endosperm nucleus and the second 

 male nucleus. 



In crosses between podded maize (maize having each grain 

 covered by husks) with common maize, the pod character proved 

 to be a dominant Mendelian factor, which segregated perfectly 

 in F 2 . 



Red sap colors appear in maize in the pericarp, the cob, the 

 husks, the silks, the glumes, and in the anthers. 



Red pericarp (R) without red on the cob or in the silk, crossed 

 with white pericarp gave three reds to one white in F 2 , the segre- 

 gation being perfect. 



