cobs were scored as grade-1, because they had long soft 
glumes which were structurally similar to the carbonized 
ones from the original Chapalote in the previous level. 
Some of the soft-glumed cobs were also identical in all 
other characteristics to the original specimens except in 
being non-carbonized. Therefore, the continuity of the 
population of cobs was not completely broken by the 
change to Tripsacoid maize. 
The sudden change to these Tripsacoid cobs of Level 
4 does not preclude a change in maize background from 
that of the original Chapalote. ‘Teosinte introgression 
had already occurred much earlier in the Chapalote from 
other parts of New Mexico (Bat Cave in Catron County, 
Mangelsdort and Smith, 1949); it was well established 
in this race in northwestern Mexico by 750+250 A.D. 
(Mangelsdorf and Lister, 1956). Inasmuch as ‘Tripsacoid 
Chapalote was prevalent then and there is no evidence in 
type of ceramics or sandals of trade from far outside the 
area, the new variation is attributed to teosinte intro- 
gression in Chapalote. 
The onset of teosinte introgression caused a marked 
drop in the average size of cob to the lowest values for 
the site. The average kernel row-number dropped by 
11%, the cob diameter by 10%, and the cob length by 
22% below that of the original Chapalote. These reduc- 
tions represent modification toward the spike of teosinte 
and are correlated to estimated teosinte introgression in 
the population as a whole (Plate NXNTV, figs. 1, 2, 3). 
These reductions in average cob size in the Tripsacoid 
maize may not reflect a corresponding loss in over-all 
yield per plant or peracre of plants. Some modern maize 
breeders have found that a reduction in ear size in teo- 
sinte derivatives of maize tends to be compensated for by 
an increase in number of ears per plant. However, some 
of the energy in 'Tripsacoid maize may be diverted away 
