Differential pollen germination in Couroupita
guianansis (left graph) and Lecythis pisonis (right
graph). Note that in both species, no matter the concentration
of the germination medium, the pollen of the ring germinates but
that of the hood does not germinate. The hood and ring pollen
are physiologically differentiated from one another. The hood
pollen is the pollinataor reward and the ring pollen effects pollination.