588 THE AMERICAN NATURALIST. (VoL. XXXIX. 
These experiments of De Vries, Correns, Webber, and others 
have established experimentally the facts of xenia and Nawas- 
chin’s theory of double fertilization seems to offer the. only 
explanation of the phenomenon. But it was left to Guignard 
(: 01) to make the concluding observation that a second sperm 
nucleus does actually enter into the composition of the endo- 
sperm of maize, and this fact clinched the argument which up 
to this time had been a speculation. 
Webber has made a very important addition to the theory of 
“double fertilization " as an explanation of xenia in some obser- 
vations and speculations on a mottled condition which is some- 
times present when white corns are pollinated by colored. He 
found that the color was sometimes only transmitted in spots as 
when Hickory King was pollinated by Cuzco, or perhaps only 
half a kernel may be colored. Webber offers the hypothesis 
that the second sperm nucleus may enter the embryo-sac but 
instead of uniting with the two polar nuclei to form a triple 
fusion may itself divide separately and thus gives rise to a 
progeny very different from the other endosperm nuclei. 
There might then be two sets of nuclei in the endosperm one of 
which is composed of nuclei which would come directly from 
the male parent. These latter then might become distributed 
throughout the embryo-sac but would tend to remain in groups 
as multiplication progressed and would certainly be expected to 
influence the character of the tissue which is formed later when 
the walls are developed around the free nuclei. As Webber 
expresses it, there might be formed islands of tissue in the 
endosperm whose cells contain nuclei derived directly from the 
second sperm and such tissue would be expected to show char- 
acters of the male parent in spots as xenia. Again, if the sperm 
nucleus should unite with only one of the polar nuclei and the 
other should give rise to an independent progeny we should 
expect similar mixed conditions in the endosperm, with xenia 
only expressed in the areas dominated by nuclei containing 
material derived from the sperm. 
: There have been reported illustrations of xenia in tissues out- 
side of the endosperm but we are fully justified in awaiting 
their confirmation before accepting them, especially since some 
