the core sampling. The possibility of contamination by atmos- 
pheric pollen appears to be equally remote. 
The Bellas Artes site is centrally located in greater Mexico 
City, one of the largest metropolitan areas in this hemisphere. 
It is many miles removed in all directions from the nearest 
corn-growing areas. We do not know exactly how far corn 
pollen can be carried by the wind but compared to the pollen of 
some other species, pines for example, it is relatively heavy. 
Agronomists and seed producers maintaining the purity of 
breeding lots of corn allow about one thousand feet of isolation 
if the contaminating pollen comes from the windward side, less 
if physical barriers to air flow are present (26). During the time 
of year that corn pollen would be shedding in Mexico City, if 
corn were there, the air is relatively still, indeed so much so 
that industrial pollution not carried away by the wind has 
become a major problem. 
An experiment performed for another purpose by a Harvard 
graduate student, Ramana Tantravahi, may have a bearing on 
the question of how far corn pollen can travel with the wind. In 
order to effect the hybridization of teosinte with 7ripsacum on 
a large scale, Tantravahi grew emasculated plants of teosinte 
adjacent to pollen-shedding plants of Tripsacum in a small 
garden surrounded by University buildings in Cambridge. To 
test the effectiveness of the emasculation of teosinte and to 
detect contamination by corn pollen from any source he also 
grew in the garden arow of emasculated corn plants. When the 
ears of these were examined at the end of the season, not a 
single kernal was found (27), although there were extensive 
plantings of corn in the market-gardening area near the 
Waltham Field Station about six miles due west of Harvard 
University. The winds during the corn-pollen-shedding season 
are prevailingly from the west. These observations suggest that 
corn pollen cannot ordinarily be carried as far as six miles. 
The possibility that there was corn pollen in the air at the 
Bellas Artes site when the soil sampling occurred is quite 
remote. Almost equally remote is the possibility that such 
pollen, if actually there, could have contaminated the core 
samples. 
The core sampling at the Bellas Artes site that revealed the 
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