ly larger than that of New York City are found almost all 
the knob positions known in maize from any part of the 
world. Here too are the localities where Kempton and 
Popenoe (9) found teosinte occurring as the dominant 
species over thousands of acres,* the only place so far dis- 
covered where this condition exists, and where they also 
found a species of ‘Tripsacum growing in great profusion. 
Here then are all the elements to make the picture com- 
plete: Andean types of corn almost completely lacking 
in chromosome knobs, slightly contaminated descendants 
of the pure corn introduced from South America; Trip- 
sacum growing in profusion on the hillsides and furnish- 
ing the opportunity for natural hybridization; the most 
Tripsacoid type of Kuchlaena known, presumably the 
primary product of the hybridization of Zea and Tripsa- 
cum, occupying thousands of acres as the dominant spe- 
cies, and finally Tripsacoid maize varieties, secondary 
products of the hybridization, showing all degrees of ad- 
mixture with Tripsacum. 
Here then, if diversity is any criterion whatever, is cer- 
tainly a well-defined center of origin of cultivated maize. 
According to the hypothesis of Mangelsdorf and Reeves 
this is the secondary center of origin, the place where new 
types have come into existence as the result of hybridiza- 
tion of maize and 'Tripsacum. According to older hypoth- 
eses which have maize deriving directly from teosinte, or 
all three of the American Maydeae, maize, teosinte and 
Tripsacum deriving from a common ancestor, this is the 
primary center of origin of cultivated maize. In any event 
it is obviously a concentrated center of diversity not only 
in the external morphological characteristics of the ears 
* Teosinte in this area is even more common than the observations 
of Kempton and Popenoe indicate, since McBryde has found it growing 
in great abundance between Santiago Petatan and Santa Ana Huista, 
a locality about four miles west of San Antonio Huista. 
223°) 
