fore drawing conclusions about the nature of pod corn. 
The ear of Peruvian corn, which he illustrated (13) as a 
form of pod corn, proved upon further study, including 
its introduction into uniform inbred strains, to be not 
half tunicate but rather the character now known as papy- 
rescent. This character does appear to affect only the 
glumes of the pistillate inflorescence and in this respect 
differs decidedly from half tunicate which, as will be 
shown by data presented later, produces virtually all of 
the effects of tunicate, only in a lesser degree. 
We ourselves have given serious consideration to the 
possibility that half tunicate, rather than tunicate, is the 
ancestral type and that the latter may be an extreme 
form — the product of a pseudoallelic locus which has 
arisen during domestication as a mutation resulting from 
the duplication of an existing locus. We do not yet rule 
out this possibility; indeed we have for some years been 
developing stocks to determine whether the 7'w locus is 
a compound one whose elements are sometimes separated 
by crossing over to produce ‘‘mutations”’ to half tunicate. 
A preliminary experiment on this point conducted in 
the summer of 1958 produced one apparent mutation 
from tunicate to half tunicate which was accompanied 
by crossing over between the sw and g/3 loci on chromo- 
some 4. 
But whether tunicate or half tunicate is the ancestral 
form 1s of secondary importance since both are pod corn 
and both involve the 7 locus on chromosome 4. There 
can be no doubt that there have been changes at this 
locus and little doubt that these changes have been a 
factor in corn’s evolution under domestication. This is 
demonstrated by the facts set forth below. 
THe Errects oF THE ALLELES AT THE 7 Locus 
One result of our intensive study of pod corn has been 
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