Pollen differences between Stylisma and Bonamia (Convolvulaceae)

Although discounted in a monograph recognizing Stylisma as distinct from Bonamia, pollen morphology is useful in distinguishing these genera. Light and scanning electron microscopy show that the pollen of Stylisma is characterized by an advanced 3-aggrecolpate aperture totaling 12 or 15 colpi, while pollen of Bonamia is typically of a primitive 3-colpate type.