number, than between the modern representatives of 
these genera, which cross only with difficulty. Though 
there is not total agreement as to the origin of teosinte, 
there can be little doubt that it has played a major role 
in the evolution of modern maize, through hybridization 
and introgression. Mangelsdorf and his collaborators 
(123-131) have supported the hypothesis that the most 
primitive maize is both tunicate (a pod corn) and a pop- 
corn. This seems to have been supported by archaeologi- 
cal and other studies (181, 213). Mangelsdorf and Reeves 
further hypothesized that the ancestral region for maize 
should be sought in the South American lowlands, where 
some primitive forms are still found. More recent evi- 
dences seem to indicate a peripheral nature for these 
South American types. There is paleontological and 
archaeological evidence that maize is of greater antiquity 
in North America than in South America (16, 77, 181). 
Maize pollen was recovered at a depth of seventy meters 
in the Valley of Mexico; this is interpreted as represent- 
ing wild maize growing in that region in the Pleistocene 
(16, 67,77,181). Archaeological material from Bat Cave, 
New Mexico is of particular interest (181). The maize 
from the lowest level of these deposits (about 2500 to 
2000 B.C.) is a very small-eared form and appears to be 
both a pod corn and a popcorn. Cobs in later levels are 
larger and show evidences of introgression from teosinte. 
Wellhausen et al (213) have recently published a val- 
uable book on the races of maize in Mexico. They have 
recognized and characterized at least twenty-five dis- 
tinct races which are grouped into four classifications: 
‘Ancient Indigenous,’” primitive popcorns of relictual 
distribution, two of which are weakly tunicate; ‘*‘ Pre- 
Columbian Exotic,’ races believed to have been intro- 
duced into Mexico from the south in prehistoric times: 
**Prehistoric Mestizos,’* derived from races of the first 
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