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)
Genera ca. 40, species perhaps 500 (7 genera, 25 species in the flora).
|1||Blades simple, undivided.||> 2|
|1||Blades pinnatifid or pinnatisect, rarely 1-pinnate.||> 5|
|2||Sporangia confined to marginal or nearly marginal bands in distal 1/2 of blade.||Neurodium|
|2||Sporangia in discrete, round to oblong or slightly elongate sori on abaxial surface, not in marginal bands.||> 3|
|3||Blades abaxially with peltate scales.||Pleopeltis|
|3||Blades abaxially glabrous, except for scattered scales on midrib.||> 4|
|4||Stems 2-10 mm diam.; sori in 1-10 or more rows between midrib and margin; petioles clustered, proximate; main lateral veins often prominent, ±parallel.||Campyloneurum|
|4||Stems 0.5-1.5 mm wide; sori in 1 row between midrib and margin; petioles well separated, often 1-2 cm apart; main lateral veins obscure, not parallel.||Microgramma|
|5||Blades with numerous peltate or ovate scales abaxially.||Pleopeltis|
|5||Blades lacking scales abaxially except along midrib.||> 6|
|6||Blades pectinate, usually with more than (20-)25 pairs of segments; segments narrow, linear, 1.5-5(-8) mm wide; veins free; stems short-creeping; Florida.||Pecluma|
|6||Blades pinnatifid, rarely 1-pinnate, with fewer than 20(-25) pairs of segments; segments broad, generally (3-)5-20(-30) mm wide; veins free or anastomosing; stems moderately to widely creeping.||> 7|
|7||Blades 1-pinnate; Florida.||Polypodium triseriale|
|7||Blades pinnatifid.||> 8|
|8||Venation free or with 1 row of areoles between costa and margin; sori at end of 1 included veinlet or on forked free vein; widespread but not Florida.||Polypodium|
|8||Venation highly reticulate, with 3-4 rows of areoles between costa and margin; sori at end of usually 2 included veinlets; Florida.||Phlebodium|