Plants perennial, terrestrial, on rock, or often epiphytic, erect, arching, or occasionally pendent. Stems long- to short-creeping, branched or not, bearing scales and few to numerous roots, usually dictyostelic. Leaves monomorphic to dimorphic, circinate in bud. Petiole usually articulate at base [rarely nonarticulate, as in Loxogramme ], lacking scales or sometimes scaly, with usually 3 vascular bundles. Blade petiole, rachis, costae, and sometimes blade tissue usually bearing hairs (these often septate and with reddish crosswalls) and/or scales. Sori borne abaxially on veins, round to oblong, occasionally elongate, rarely marginal, rarely covering surface; paraphyses present or absent; sporangia with stalk of 2 or 3 rows of cells; indusia absent. Spores usually transparent or yellowish (rarely greenish), all 1 kind, bilateral, monolete [rarely trilete, as in some Loxogramme], surface most often smooth, tuberculate, verrucose, or granulate, occasionally spiny, 64 per sporangium (spores globose and 32 per sporangium in apogamous spp.). Gametophytes green, aboveground, cordate or elliptic, glabrous or sometimes glandular; archegonia and antheridia borne on lower surface, antheridia 3-celled.

Genera ca. 40, species perhaps 500 (7 genera, 25 species in the flora): worldwide, especially tropics and subtropics.

Phymatosorus scolopendria (Burman f.) Pichi-Sermolli, native to the Old World, is a rare escape in southern Florida. Genera in this family are variously circumscribed, and the New World species historically were placed in the single genus Polypodium . Many of the segregates recognized here are still placed in Polypodium in recent floristic accounts. Limits of genera in both Old World and New World are controversial and are currently under study by several workers.

(Key to genera of Polypodiaceae)

PLANT: Perennial herbs with branched or unbranched rhizomes, these scaly and often pruinose or glaucous, the scales sometimes clathrate (“resembling latticework”). ROOTS: adventitious, usually branched. AERIAL STEMS: absent. LEAVES: closely or widely spaced along the rhizome, often attached at a joint to a low peg like protrusion of the rhizome (phyllopodium), ours monomorphic, the vernation circinate. PETIOLES: with usually 3 small vascular bundles basally. BLADES: pinnatisect in ours, usually at least somewhat coriaceous, distally usually somewhat pinnatifid. VENATION: free or more commonly casually to regularly anastomosing, sometimes difficult to observe. SORI: on the abaxial leaf surface, surficial or from shallow pits in the blade surface, often restricted to the distal half of the blade, discrete in ours, in a single row on each side of the costa in ours, circular to oblongelliptic in outline. INDUSIA: absent. PARAPHYSES: sometimes present among the sporangia, peltate or clavate. SPORANGIA: with a stalk 2 or 3 cells wide, the capsule with a vertical ring-like annulus. SPORES: 64 per sporangium, monomorphic, monolete, bean-shaped, usually yellow. GAMETOPHYTES: surficial, cordate, green, usually glabrous, potentially bisexual. NOTES: Ca. 40 genera and 500 spp., nearly worldwide. The Polypodiaceae, which at one time were circumscribed to comprise most of the more advanced groups of ferns, are here treated in a more restricted sense. Generic classification within the family continues to undergo revision. The family is most diverse in the tropics, and is an important component of epiphytic vegetation in many forest types. REFERENCES: Yatskievych, G. and M.D. Windham. Vascular Plants of Arizona: Polypodiaceae. CANOTIA 5 (1): 34–38, 2009.