Other specimens occurred in the two succeeding phases. 
Several of these comprised clusters of spikes (Plate XII, 
A). 
The specimens which we identified as maize-teosinte 
hybrids differed from those of teosinte in having thicker 
stalks and non-fragile rachises. The one illustrated in 
Plate XII, B is of particular interest in resembling spikes 
which we have produced by introducing one of the tuni- 
cate alleles into teosinte thereby replacing the highly in- 
durated lower glume of teosinte with the herbaceous 
glume of tunicate maize. When we first encountered 
this specimen we wondered briefly whether it might rep- 
resent the ancestral form of corn postulated by the late 
R. A. Emerson: a soft-shelled form of teosinte.* Be- 
cause these specimens were borne on thicker stalks than 
the clusters of teosinte we concluded that they were 
maize-teosinte hybrids. 
Wecannot be certain whether the specimens identified 
as maize-teosinte hybrids are F; hybrids or segregates 
appearing in subsequent generations. They resemble F 
hybrids in their non-shattering rachises but differ from 
typical modern F; hybrids in having single rather than 
paired spikelets. 
The presence in the caves of remains of teosinte is 
puzzling. The seeds of teosinte are nutritious, having a 
higher protein content than those of corn (Melhus ef al., 
1953), but are enclosed in hard bony shells from which 
they are difficult to remove. Although this can be done 
by popping if the moisture content of the seeds is right 
(Beadle, 1939) there is no evidence from the prehistoric 
remains that teosinte was used in this way. On the con- 
trary Dr. E. O. Callen, who has made a study of the 
feces from these caves, has found a number of teosinte 
fruits with their hard bony shells still undamaged or un- 
* In conversation. 
[ 46 ] 
