which have increased in size and corresponding pore- 
axis ratio as a result of preservation under rather 
unusual sedimentary conditions. There is obviously 
no way to prove that this is not true, but if it were 
the case, it would be totally inconsistent with pre- 
vious extensive experience by numerous investi- 
gators in dealing with Pleistocene and Tertiary 
microfossils. 
The pollen grains are those of ancient maize. This 
appears to be the most reasonable interpretation 
and certainly from the evidence now at hand the 
only plausible one. The large fossil grains resemble 
maize pollen not only in their general appearance 
but in their size, and when it can be determined, 
in their pore-axis ratio. They differ somewhat from 
pollen grains of modern maize in possessing a slight- 
ly thicker exine and, more significantly, a smoother 
contour in folding. Although these differences may 
be due in part to conditions of preservation and 
post depositional change, it is of interest to note that 
the prehistoric pollen from Bat Cave, New Mexico 
shares these properties to some extent; but they are 
less evident in modern maize (Plate XX XVIII). 
Only one of the well preserved grains from the lower 
levels does not fall within the range of Tripsacum or 
maize. This grain measures 70.5 in length, with a pore- 
axis ratio of 4.7, which is outside the range of maize as 
determined by our measurements. In pore-ratio it is just 
within the extreme for Tripsacum and the lower range 
for teosinte. Whether this one specimen represents an 
unusually large grain of Tripsacum, other grains of which 
have been found at this level, or a slightly atypical grain 
of teosinte, cannot be determined. There remains a re- 
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