1913] EAST—XENIA AND ENDOSPERM 221 
to several conclusions indicated by the experiments. It is evident 
that in the varieties of maize used, a paternal and a maternal 
nucleus carrying the same hereditary factors as are borne by the 
true gametes—in the case of the 7 factors investigated—always 
fuse in the formation of the endosperm. For this reason geneticists 
investigating maize have been correct in treating the endosperm as 
if it were an-embryo. The endosperm characters have behaved 
exactly like plant characters. Two white varieties of sweet peas 
may carry factors both-of which are necessary for the production 
of color. When they are crossed, color develops. Color develops 
in maize in a quite similar manner when the two complementary 
factors are carried by the “endosperm nucleus” and the second 
male nucleus. Nevertheless, one should keep in mind that the 
problem is complicated. Coxxrns (1) found a white ear of maize 
in a yellow variety that behaved as if its seeds were crossed with 
the yellow. He interpreted the phenomenon as a mutation showing 
reversal of dominance, although the data on succeeding generations 
corroborated those obtained by previous investigators in which 
yellow was partially or completely dominant. It is not unlikely, 
however, that CoLLins merely happened upon a plant from white 
seed in which the male nucleus did not enter into the formation of 
the endosperm, although other interpretations are possible. This 
may seem like an odd statement after having shown that the two 
nuclei always fuse, but it is made advisedly. In most varieties of 
maize the two nuclei do appear always to fuse, but Haves is now 
working out the details in a cross in which a Mexican starchy corn 
is one of the parents where the nuclei appear never to fuse. In 
other words, it seems that there may be varieties of maize in which 
endosperm formation is the opposite of that just described, and 
within each category mo change to the other has been found. But 
may not such a change occur ? 
Whether or not the last suggestion ever proves to be true, it 
seems to me that from the data now collected one is entitled to 
discuss angiosperm endosperm formation from the viewpoint of 
experimental genetics. 
The endosperm of the gymnosperms is essentially vegetative 
tissue of the female gametophyte. It results from continuous cell 
