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AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
colored and non-shrunken, C Sh, except for a single large spot that was 
both colorless and shrunken (fig. i, G). The sperm in this case must have 
carried both C and Sh, for otherwise the seed would have been colorless 
and shrunken throughout. The evidence, therefore, so far as this one 
seed is concerned, is definitely in favor of the hypothesis of aberrant chromo- 
some behavior and opposed to that of somatic mutation. 
Both / i and Wx wx are without doubt concerned in the case of a single 
aberrant seed reported by G. N. Collins (1913). A colored waxy type 
pollinated by a colorless corneous one resulted in colorless corneous seeds. 
The dominance of the colorless condition establishes, so far as is now known, 
the presence of / in the colorless pollen parent. A single seed of this cross, 
though colorless and corneous in the main, had a small spot of colored 
aleurone which overlaid exactly a spot of waxy endosperm. It seems 
evident that in this one instance in which an aberrant seed involved the 
linked factors / pnd Wx, just as in the single case in which C and Sh were 
involved and in the great majority of the cases — 55 out of 58 — ^in which 
the linked factors C and Wx were concerned, aberrant endosperm develop- 
ment is ordinarily due to some unusual chromosome behavior possibly of 
the nature of non-disjunction. 
One unfamiliar with some of the results previously published will not 
have failed to observe by this time that either one of Webber's (1900) well- 
known hypotheses might account for the results presented above quite as 
well as the hypothesis of non-disjunction. Webber, it will be recalled, 
suggested as possible explanations of aberrant endosperm development 
(i) that the second sperm nucleus on the one hand and the fused polar 
nuclei on the other may occasionally develop independently, each giving 
rise to a part of the endosperm, or (2) that the second sperm nucleus may 
sometimes unite with one polar nucleus, leaving the other polar nucleus 
to develop independently. If either of these things should happen, it is 
obvious that, in cases of aberrant endosperm where C and Wx come from 
the male and c and wx from the female parent of a cross, the colored parts 
must be corneous and the colorless ones waxy. The second sperm nucleus, 
carrying C and Wx, whether it divide independently or unite with one polar 
nucleus, would give rise to colored corneous endosperm, and the endosperm 
developed either from one polar nucleus alone or from a fusion of the two, 
both carrying c and wx, would produce colorless waxy endosperm. 
But it was shown by East (1913) that Webber's first hypothesis, inde- 
pendent development of the sperm nucleus and of the fused polar nuclei, 
was untenable. Crosses were made between two types of maize, both with 
colorless aleurone but one having factor C and the other having factor R, 
both of which are essential to aleurone-color development. Among the 
numerous colored seeds resulting from these crosses, six were colored on 
one side and colorless on the other. It is obvious that these aberrant seeds 
could not have arisen in accordance with Webber's first hypothesis, for, 
