Structures that receive sporopollenin are similar in the pollen grains
of a wide variety of angiosperms and in the conifer Pinus. These stru
ctures are rod-shaped, with a central core that accepts stains strongl
y and an outer binder zone that only weakly accepts stains. These spor
opollenin-accumulating rods are substructures of the exine units we ca
ll ''tufts''. In many taxa tuft substructures are covered by receptor-
independent (extra-tuft) accumulated sporopollenin and surfaces are sm
ooth. We show an example (Quercus coccifera) of the acetolysis resista
nce of extra-tuft accumulated sporopollenin followed by its removal th
rough oxidation which reveals the tufts.