Andr. Matthioli Comm. Polypodium Alternum in gold frame with Pale Laurel mat Measures 22 W x 28 H x 1 D Polypodium is a genus of ferns in the family Polypodiaceae, subfamily Polypodioideae, The genus is widely distributed throughout the world, with the highest species diversity in the tropics. They are terrestrial or epiphytic ferns, with a creeping, densely hairy or scaly rhizome bearing fronds at intervals along its length.