Sporoderm development has been studied in several species of polypodiaceous ferns belonging to the genera Microgramma Presl and Belvisia Mirbel. Both transmission and scanning electron microscopy have been applied, the latter technique including freeze-fracturing. This has shown a different succession of ontogenetic spore surface patterns in the two genera. For each genus, the ontogenetic series observed is also compared with mature spore surfaces in other congeneric species.