The pollen grain morphology of 40 specimens (19 species) of Dorstenia was examined by light microscopy and, for a smaller numer of species, by transmission and scanning electron microscopy. It was not possible to distinguish each species, on the basis of a particular pollen grain morphology. However, three pollen sub-types were established in relation to the number of pores; within the first, it was possible to separate D. brasiliensis, with psilate aspides, from other related species, having spinulate aspides. With regard to surface confíguration and the number of pores per grain, no correspondence was found between the pollen sub-types and established taxonomic sections. Aperture construction was elucidated by ultra-thin sections and the special aspect of D. brasiliensis pollen grains is here emphasized. Evolutionary trends among the species examined are discussed, based upon number of pores and exine stratification and ornamentation
