PLATE 18 
Plate 18. The effect of the acetolysis treatment on restoring pollen to its original 
shape. A. Modern pollen grain of the Mexican popcorn race Polomero Toluqueno, fully 
expanded after treatment: B. Archaeological pollen grain from the Tehuacan site, 
Mexico ca 1600 years old, expanded: C. Pollen grain ca 1900 years old from the same 
site, slightly collapsed; D. Fossil pollen grain from the Bellas Artes site, Mexico, 
completely collapsed, showing that it is ancient and does not represent contamination 
of the core samples. 
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