The surface of the upper glumes, like that of the lower, 
may be glabrous, hispid, or hairy, although the two 
glumes are not necessarily identical with respect to these 
characteristics. Only glabrous upper glumes were found 
in Stratum I and glabrous glumes continued to predom- 
inate throughout all strata. Hairy upper glumes made 
their first appearance in Stratum II and increased in fre- 
quency in successive strata up to V. Hispid upper glumes 
first appeared in III and occurred in small percentages 
in the remaining strata. 
The visible venation of the upper glume is strongly 
but not completely correlated with its shape and texture. 
The data on venation of the upper glume in this material 
are generally in agreement with the data on shape and 
texture. Strongly veined glumes, like those which are 
boat-shaped or chaffy, have their lowest frequency in 
Stratum V. 
Tunicate Alleles. An attempt was made to classify 
the cobs with respect to the degree to which they were 
tunicate or non-tunicate. As has already been mentioned, 
four degrees of tunicate— Tu, tuk, tww, and tu—are 
known and a fifth, tw intermediate between fu’ and 
tuw, is believed to occur. 
No cobs with glumes as strongly developed as those 
of modern pod corn of the genotype Tutu were found, 
but true pod corn of the half-tunicate type occurred in 
each of the six strata. Pod corn of the fourth-tunicate 
type also occurred in all strata and indeed was the most 
common type in all except the uppermost. Weak-tuni- 
cate first appeared in Stratum III and became the most 
common type in VI. Only one ear regarded as non- 
tunicate was encountered. 
These data indicate strongly that one of the principal 
factors involved in the evolution of maize has been a 
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