of maize under domestication is further supported by the 
occurrence— more widespread than had previously been 
suspected—of various forms of pod corn among the living 
varieties of this hemisphere. The extreme form condi- 
tioned by the Zw gene has been found in Colombia, 
Brazil, Peru and Bolivia. It is apparently quite common 
in Bolivia where, according to a report from Senor Dick 
Edgar Ibarra Grasso, Director, Museo Arqueoldégico, 
Universidad Mayor de San Simon, Cochabamba, Bolivia, 
it occurs in many of the valleys on the eastern slopes of 
the Andes. 
The half-tunicate form of pod corn controlled by the 
tu’ locus has appeared in varieties from Ecuador, Para- 
guay and Peru (14). It, or something like it, is rather 
common in a Peruvian coastal race, Perla. Mr. Alexan- 
der Grobman of the National School of Agriculture near 
Lima has reported that one to two percent of the inbred 
strains isolated from this race are segregating for half- 
tunicate ; insome collections the frequency is even higher. 
How is this situation to be explained? Either wild corn 
was pod corn and had the genotype 7'u7'w or tu'tu’ or 
it was not and had the genotype tutu. If it was not pod 
corn, then the 7'w and tu? genes now found in corn must 
represent mutations from the lower allele to the higher 
alleles in the series. Mutations from lower to higher al- 
leles do occur but are not common. More difficult to ex- 
plain is the preservation of these higher alleles if they are 
not the original ones. We can perhaps imagine that the 
pod corn controlled by the 7'w allele was preserved by 
man as a curiosity or for its supposed magical properties, 
but this could scarcely be true of the weak pod corn con- 
trolled by the tu’ gene since in the heterozygous condi- 
tion it is not generally recognized. Yet, because of com- 
petition between glumes and kernels, the weak pod corn 
undoubtedly causes some reduction in the yield of grain 
[ 348 ] 
