Any of a number of ferns of the family Polypodiaceae and particularly of the genus Polypodium. Well represented in the North Country by 28 species in 15 genera, including the Common Polypody or Rock Fern ( Polypodium virginiana), commonly found growing in large patches on the surface of boulders. From the Greek, polus ( polus), "many", and podion ( podion), "foot", from the numerous branches of the rootstalk.