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

pantoporate, annulus around pores not visible; psilate

zonoporate , 4 to 5 pores; rugulate, roundish, slightly angular pollen grain ("golf ball")