appears to be the more plausible one. The senior author 
(1946) suggested several years ago that much of the re- 
cent evolution in maize has been a matter of absorbing 
the morphological assets of teosinte while suppressing its 
morphological liabilities through selection for appropri- 
ate modifier factors. The material from Bat Cave is al- 
most direct evidence in support of this thesis. 
The interaction between the various alleles of Ju and 
the introgression of teosinte germplasm is an interesting 
one which is clearly revealed by some of the cobs in 
Strata IV and V. In a recent paper (1948) the senior 
author illustrated a spike of tunicate teosinte produced 
by introducing the 7 gene into teosinte through re- 
peated back-crossing. The rachis was reduced to a slen- 
der disarticulating stem. The prominent glumes, quite 
distinct from the bony glumes of teosinte in size and 
structure, had, nevertheless, taken on a coriaceous quality 
very different from the papery or chaffy glumes of pod 
corn. They seemed almost to be a product of distributing 
over a large volume of tissue all of the factors for hard- 
ness and stiffness ordinarily found in a small volume. 
Teosinte introgression has similar effects upon geno- 
types representing lower alleles in the 7'w-tu series. Plate 
XXVI, Figs. F, G, H, illustrates three cobs from Bat 
Cave which are similar, if not identical, with respect to 
their alleles of Z'u, but which differ decidedly in the 
amount of teosinte introgression. 
Evidence for introgression of teosinte germplasm into 
maize was not confined to a general increase in the hard- 
ness of the rachis and outer glumes, since individual char- 
acteristics of teosinte also made their appearance. Three 
cobs were found with the distichous arrangement charac- 
teristic of teosinte. These occurred in Strata IV, V, and 
VI. ‘Two cobs were found which bore single spikelets, 
also a teosinte characteristic. These occurred in Strata 
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