the fossil pollen (/, 6, /6) but with equal unanimity have over- 
looked or ignored the statement set forth rather conspicuously 
in these authors’ summary that their data **do not refute the 
findings of Barghoorn et a/.’* and that five of the fossil pollen 
grains studied by Barghoorn ef al. “‘are sufficiently large in 
both axis length and pore diameter as well as axis/pore ratio to 
be classified as maize with a high degree of reliability.” 
IDENTIFICATION OF THE FOSSIL POLLEN 
The problem of identifying the fossil pollen is one of compar- 
ing it with the pollen of corn and its two American relatives 
teosinte and Tripsacum. There are no other native grasses with 
which the fossil pollen might be identified. Distinguishing the 
fossil pollen from that of Tripsacum is not difficult since there is 
litte overlapping in size, only the largest grains of Tripsacum 
being within the range of the smallest grains of corn. Also the 
pattern of spinules on the exines of 7ripsacum grains, as re- 
vealed by the scanning electron microscope, is quite different 
from that in corn. In Tripsacum the spinules occur in clusters: 
in corn they are regularly distributed as they are also in teosinte 
(17, 18). 
Since the pollen of corn can not be distinguished from teo- 
sinte pollen by their spinule patterns which are quite similar, 
the only criterion for making a distinction is one of size. It has 
been asserted that size is not a taxonomic character. This is not 
strictly true. The principal difference between popcorn and 
flint corn, for example, is in the size of their kernals. Size of 
structures is often included as a part of taxonomic descriptions. 
In certain instances there is no difficulty in distinguishing 
corn and teosinte pollen by size alone. For example, ina recent 
publication (/8), the photographs of pollen of Guerrero teosinte 
and Confite Morocho corn show the corn pollen to be only 
slightly larger than the teosinte pollen. But when the corn 
pollen is enlarged to the same magnification, x 1692, as the 
teosinte pollen it proves to be half again as long as the teosinte 
pollen with about twice the volume. 
Although individual grains of corn pollen cannot always, as 
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