GENETIC EVIDENCE OF ABERRANT CHROMOSOME 
BEHAVIOR IN MAIZE ENDOSPERMi 
R. A. Emerson 
(Received for publication February 26, 192 1) 
The occasional appearance of a maize seed, the endosperm of which 
is in part colored and in part colorless or in part starchy and in part sugary, 
has long been known, and much speculation has been indulged in by 
geneticists in attempts to account for the phenomenon. Some years ago 
the writer (Emerson, 191 5) reviewed the hypotheses that had been pre- 
viously offered as possible explanations of such seeds and suggested the 
further hypothesis of somatic mutation, a suggestion that has been repeated, 
apparently independently, by J. L. Collins (1919). It was noted also that 
irregular chromosome behavior might possibly be concerned. In a later 
paper (Emerson, 191 8) numerous cases of anomalous endosperm develop- 
ment were reported and discussed in relation to the hypotheses of somatic 
mutation and of aberrant chromosome behavior. It was pointed out that 
the facts then at hand could be accounted for equally well by either of the 
two hypotheses, and the kind of evidence necessary for a crucial comparison 
of the two was noted. 
In the latter paper evidence was presented that tended to prove that 
aberrant seeds are not produced (i) when the dominant endosperm factor 
concerned, for example the aleurone-color factor C, is homozygous and 
therefore triplex, C C C, or (2) when the dominant factor is brought into 
the cross by the female parent and its recessive allelomorph by the male 
parent, C C c, but only (3) when the dominant factor is contributed by the 
male alone, c c C. In the case of either C C C or C C c, a- single mutation 
from the dominant to its recessive allelomorph could result only in C C c 
or C c c, respectively, and the aleurone would still be colored and no ap- 
parent anomaly would result. To produce colorless aleurone, c c c, two 
mutations in case of C C c and three in case of C C C must occur simul- 
taneously or successively in the endosperm of the same seed — a chance so 
small that it might well be disregarded. It was noted that a single dominant 
mutation from c to C should change colorless, c c c, to colored, C c 
aleurone, but the relative infrequency of dominant mutations was thought 
to account for the lack of observed aberrant seeds in homozygous colorless 
types. 
Similarly, it was noted that if a single non-disjunction of the chromo- 
some carrying C or c occurred, it could not result in a visible change in 
aleurone color in case of such genotypes as C C C, C C c, or c c c, but only 
^ Paper No. 86, Department of Plant Breeding, Cornell University, Ithaca, New York. 
411 
