Polypodium

Polypodium is a genus of ferns in the family Polypodiaceae, subfamily Polypodioideae, according to the Pteridophyte Phylogeny Group classification of 2016 (PPG I). The genus is widely distributed throughout the world, with the highest species diversity in the tropics. The name is derived from Ancient Greek poly ("many") + podion ("little foot"), on account of the foot-like appearance of the rhizome and its branches. They are commonly called polypodies or rockcap ferns, but for many species unique vernacular names exist.

They are terrestrial or epiphytic ferns, with a creeping, densely hairy or scaly rhizome bearing fronds at intervals along its length. The species differ in size and general appearance and in the character of the fronds, which are evergreen, persisting for 1–2 years, pinnate or pinnatifid (rarely simple entire), and from 10 to 80 cm or more long. The sori or groups of spore-cases (sporangia) are borne on the back of the frond; they are globose and naked, not covered with a membrane (indusium).

Polypodies have some use in herbalism, but are today most important in horticulture where several species, hybrids, and their cultivars like Polypodium 'Green Wave' are commonly used as ornamental plants for shady locations. Polypodium have a bitter-sweet taste and are among the rather few ferns that are used in cooking; in this case as a spice e.g. for nougat.

Species
Several of the species form hybrids with other species in the genus; these may often be distinguished by being sterile, with very small "blind" sori. , Checklist of Ferns and Lycophytes of the World accepted the following species and hybrids:


 * Polypodium abitaguae Hook.
 * Polypodium aequale Maxon
 * Polypodium alavae A.R.Sm.
 * Polypodium amorphum Suksd. – irregular polypody
 * Polypodium appalachianum Haufler & Windham – Appalachian polypody or Appalachian rockcap fern
 * Polypodium arcanum Maxon
 * Polypodium × aztecum Windham & Yatsk.
 * Polypodium californicum Kaulf. – California polypody
 * Polypodium calirhiza S.A.Whitmore & A.R.Sm.
 * Polypodium cambricum L. – southern polypody, limestone polypody, or Welsh polypody
 * Polypodium castaneum Maxon ex Tejero
 * Polypodium chionolepis Sodiro
 * Polypodium chirripoense Lellinger
 * Polypodium christensenii Maxon
 * Polypodium colpodes Kunze
 * Polypodium conterminans Liebm.
 * Polypodium diplotrichum Mickel & Beitel
 * Polypodium eatonii Baker
 * Polypodium echinolepis Fée
 * Polypodium × encumeadense (Neuroth, Jäger & Bennert) F.J.Rumsey, Carine & Robba
 * Polypodium ensiforme Thunb.
 * Polypodium eperopeutes Mickel & Beitel
 * Polypodium exsul Mett. ex Kuhn
 * Polypodium fauriei Christ
 * Polypodium fissidens Maxon
 * Polypodium flagellare Christ
 * Polypodium × font-queri Rothm.
 * Polypodium fraternum Schltdl. & Cham.
 * Polypodium glycyrrhiza D.C.Eaton licorice fern, many-footed fern, and sweet root
 * Polypodium haitiense Urb.
 * Polypodium × hemipin–natum (Tejero, Mickel & A.R.Sm.) comb. ined.
 * Polypodium hesperium Maxon – western polypody
 * Polypodium hispidulum Bartlett
 * Polypodium × huancayanum G.Kunkel
 * Polypodium × incognitum Cusick
 * Polypodium interjectum Shivas
 * Polypodium iranicum Mazooji
 * Polypodium kamelinii Shmakov
 * Polypodium khasyanum Hook.
 * Polypodium longipetiolatum Brade
 * Polypodium macaronesicum Bobrov
 * Polypodium × mantoniae Rothm.
 * Polypodium martensii Mett.
 * Polypodium moricandii Mett.
 * Polypodium moritzianum Link
 * Polypodium otites L.
 * Polypodium oxylepis C.Chr.
 * Polypodium pellucidum Kaulf.
 * Polypodium pellucidum Kaulf. f. opacum (Hillebr.) D.D.Palmer
 * Polypodium pinnatissimum R.C.Moran
 * Polypodium plectolepidioides Rosenst.
 * Polypodium plesiosorum Kunze
 * Polypodium pleurosorum Kunze ex Mett.
 * Polypodium praetermissum Mickel & Tejero
 * Polypodium puberulum Schltdl. & Cham.
 * Polypodium rhodopleuron Kunze
 * Polypodium riograndense Lindm.
 * Polypodium × rothmaleri Shivas
 * Polypodium ryanii Kaulf.
 * Polypodium saximontanum Windham
 * Polypodium × schneideri G.Schneid.
 * Polypodium scouleri Hook. & Grev. – leathery polypody, Scouler's polypody, coast polypody, and leather-leaf fern
 * Polypodium sibiricum Sipliv.
 * Polypodium subpetiolatum Hook.
 * Polypodium trinidadense Jenman
 * Polypodium ursipes Moritz ex C.Chr.
 * Polypodium × vianei Shmakov
 * Polypodium virginianum L. – rock polypody, rock cap fern, or common polypody
 * Polypodium vulgare L. – common polypody

A number of species formerly included in the genus have recently been transferred to other genera, including Campyloneurum, Cyathea, Microgramma, Nephrolepis, Pecluma, Phlebodium, Pleopeltis and Serpocaulon. Species placed elsewhere include:
 * Polypodium argyrolepis = Serpocaulon lasiopus
 * Polypodium mindense = Serpocaulon eleutherophlebium
 * Polypodium mixtum = Pleopeltis murora
 * Polypodium piligerum = Moranopteris achilleifolia
 * Polypodium punctatum Thunb. ex Murray = Hypolepis punctata
 * Polypodium quitense = Pecluma dulcis
 * Polypodium rimbachii = Serpocaulon sessilifolium
 * Polypodium scutulatum = Serpocaulon fraxinifolium