unrelated eight-rowed race of maize which survives in 
mixed form ina race called Harinoso de Ocho in north- 
western Mexico (Mangelsdorf and Lister, 1956). 
Chapalote reached the Bat Cave area in New Mexico 
apparently from central or southern Mexico perhaps as 
early as 83600 B.C. (Mangelsdorf, 1954), and, after a grad- 
ual evolutionary change leading to increased size of ear 
and increased number of kernel-rows, it became the 
Basketmaker maize which formed the subsistence base 
of the prehistoric Pueblo culture. The addition or intro- 
gression of teosinte germplasm into Chapalote occurred 
probably not later than 500 B.C. at Bat Cave (Mangels- 
dorf and Smith, 1949), and it seems to have spread as 
far north as Durango, Colorado by A.D. 46 to 330 (tree 
ring dates), as will be discussed later. The degree of such 
teosinte introgression can be estimated in archaeological 
cobs, and such estimates have been correlated with vari- 
ous changes in the morphology of the cob (Galinat ef al., 
1956; Galinat and Ruppé, 1961). The effects of this teo- 
sinte germplasm include a tremendous increase in varia- 
bility and an apparent heterotic effect on ear size as well 
as an increase in drought resistance which was necessary 
for an extension of maize culture into new and more arid 
regions. 
Greater drought resistance in teosinte-contaminated 
maize may be of either a physiological or a morphologi- 
cal nature. The type of drought resistance derived from 
teosinte germplasm in maize reported by Reeves (1950) 
is apparently physiological. A morphological type of 
drought resistance in teosinte itself has been observed 
recently by Mr. Garrison Wilkes (personal communica- 
tion), and this type may also be transferred to maize. 
After examining Mexican maize fields that showed seri- 
ous drought damage and which contained Chaleo teo- 
sinte, Mr. Wilkes concluded that the teosinte was more 
[ 118 ] 
