brids are more highly lignified and more dense than those 
of ordinary maize, it was hoped that a fairly direct esti- 
mate of teosinte introgression might be made by deter- 
mining the specific gravity of the cobs. This proved for 
various reasons (for example, the presence or absence of 
pith) not to be the case. Nevertheless, it was found that 
in modern maize the specific gravity increases with known 
additions of teosinte germplasm; and that, among arch- 
aeological cobs, the Tripsacoid specimens have a signifi- 
cantly higher specific gravity, on the average, than the 
non-Tripsacoid ones. 
Specific gravity was determined by liquid displace- 
ment, using a ten percent solution of alcohol as the liq- 
uid. The modern maize tested comprised single crosses 
of the inbred strains K155, L317, 701 and 88-11 with 
4R-3 and with modified strains of 4R-8, in which two 
or three chromosomes of teosinte had been introduced 
through repeated backcrossing. 
The data (Table I) indicate a significant positive rela- 
tionship between degree of teosinte introgression and 
specific gravity. The more Tripsacoid cobs, in this case 
those known to have teosinte introgression, have a signi- 
ficantly higher specific gravity than the controls. 
In archaeological maize, a parallel experiment was con- 
ducted by substituting estimates of the induration of the 
Taste I, Average specific gravity of cobs as compared 
to number of teosinte chromosomes in modern maize 
and degree of induration in archaeological maize. 
Modern Cobs Archaeological Cobs 
No. teosinte Grade of 
chromosomes Av. sp. grav. induration Av. sp. gray. 
0 .620 2 .658+.01 
2 .680 3 .657+.01 
3 .740 4. .690+.01 * 
* Grade-4 is significantly greater than either grades-2 or 3 
[ 104 ] 
