monoporate, pore with distinct annulus; psilate, roundish pollen grain < 40 µm

zonoporate (4-5 pores), pores slightly elongated without vestibulum (otherwise very similar to Alnus); distinctly protruding annulus; psilate, dorso-ventrally flattened pollen grain

pantoporate, pores with regular annulus and operculum (lid); round, verrucate pollen grain