others as T'ripsacum. None of the intermediate or teo- 
sinte type have so far been located. This lends support 
to the thesis that wild maize existed in the Valley of 
Mexico during late Pleistocene time (Mangelsdorf 1958). 
In addition, our investigations have led to the follow- 
ing conclusions. 
1. Observations on the general similarity of maize and 
teosinte pollen supports the thesis that teosinte is a race 
of maize derived from hybridization with Tripsacum 
(Mangelsdorf and Reeves 1939). 
2. The more primitive races of maize (Puno, Chapa- 
lote, etc.) show the strongest, most regular pattern. 
3. Inbred maize strains, Minnesota A158, and Texas 
4R3, have a regular strong pattern, while the introduc- 
tion of teosinte germ plasm causes them to lose the 
strength and regularity of the pattern, Plate VI. 
4. Fossil maize from Bat Cave, New Mexico, shows 
a well defined, strong and regular pattern. ‘This maize 
pollen dates from about 5000 years ago. 
5. Several grass pollen grains, with size measurements 
in the Zea range were isolated from sediments from Lake 
Petenxil in Guatemala. Those were present in the lowest 
sample of aseries of cores taken for Harvard University 
by Dr. George Cowgill (now of Brandeis University). 
This core was radiocarbon dated by the Humble Oil 
geochemical laboratory at 8,950+ 130 years ago. The 
strength and regularity of the exine pattern suggest that 
these grains are maize. Present archaeological knowledge 
indicates that maize may have been grown in Guatemala 
at this date. The grains, however, could represent possi- 
bly wild maize types at that time still extant in the Lake 
Petenxil area. 
43 ] 
