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Leptosporangiate ferns are the largest group of living ferns, including some 11000 species worldwide. They constitute the subclass Polypodiidae,〔Christenhusz, M.J.M., Zhang, X.C. & Schneider, H. (2011). "A linear sequence of extant families and genera of lycophytes and ferns" Phytotaxa 19: 5-22〕 but are often considered to be the class Pteridopsida or Polypodiopsida,〔Smith, A. R., K. M. Pryer, et al. (2006). "A classification for extant ferns." Taxon 55(3): 705-731〕 although other classifications assign them a different rank. The leptosporangiate ferns are one of the four major groups of ferns, with the other three being the Eusporangiate ferns comprising the marattioid ferns (Marattiidae, Marattiaceae), the horsetails (Equisetiidae, Equisetaceae), and whisk ferns and moonworts.〔〔 There are approximately 8465 species of living leptosporangiate ferns, compared with about 2070 for all other ferns, totalling 10535 species of ferns.〔 Almost a third of leptosporangiate fern species are epiphytes.〔Schuettpelz, Eric. "Fern Phylogeny Inferred from 400 Leptosporangiate Species and Three Plastid Genes," contained in "The Evolution and Diversification of Epiphytic Ferns." Doctoral dissertation, Duke University. 2007. http://dukespace.lib.duke.edu/dspace/bitstream/10161/181/1/D_Schuettpelz_Eric_a_052007.pdf〕 These ferns are called ''leptosporangiate'' because their sporangia arise from a single epidermal cell and not from a group of cells as in eusporangiate ferns (a polyphyletic lineage). The sporangia are typically covered with a scale called the indusium, which can cover the whole sorus, forming a ring or cup around the sorus, or can also be strongly reduced to completely absent. Many leptosporangiate ferns have an annulus around the sporangium, which ejects the spores. ==Classification== Leptosporangiates include the vast majority of extant ferns. Only groups that branched off early from the fern lineage, which retain a eusporangium, are not included. Multiple attempts have been made to classify ferns. The classification scheme proposed by Smith et al. 2006 is the most widely accepted. More recent analyses by and Christenhusz et al. 2011 〔 and Christenhusz & Chase 2014 〔 offer additional insight into the group. *Order Osmundales (royal ferns) * *Family Osmundaceae (4 genera, ca 25 species) *Order Hymenophyllales (filmy ferns and bristle ferns) * *Family Hymenophyllaceae (2 genera, ca 650 species) *Order Gleicheniales * *Family Gleicheniaceae (incl. Dicranopteridaceae, Stromatopteridaceae) (6 genera, ca 165 species) * *Family Dipteridaceae (incl. Cheiropleuriaceae) (2 genera, 9 species) * *Family Matoniaceae (2 genera, 4 species) *Order Schizaeales * *Family Schizaeaceae(incl. Anemiaceae, Lygodiaceae, Mohriaceae) (4 genera, 190 species) *Order Salviniales * *Family Marsileaceae (incl. Pilulariaceae) (3 genera, ca 65 species) * *Family Salviniaceae (incl. Azollaceae) (2 genera, ca 20 species) *Order Cyatheales * *Family Cyatheaceae (incl. Alsophilaceae, Cibotiaceae, Culcitaceae, Dicksoniaceae, Hymenophyllopsidaceae,〔Christenhusz, M.J.M. (2009). "New combinations and an overview of Cyathea subg. Hymenophyllopsis (Cyatheaceae)" Phytotaxa 1: 37-42〕 Lophosoriaceae, Loxsomataceae, Metaxyaceae, PlagiogyriaceaeThyrsopteridaceae) (14 genera, ca 700 species) *Order Polypodiales * *Family Cystodiaceae〔 (a single species, ''Cystodium sorbifolium'') * *Family Lonchitidaceae〔 (1 genus, 2 species) * *Family Lindsaeaceae (6 genera, ca 220 species) * *Family Saccolomataceae (2 genera, ca 12 species) * *Family Dennstaedtiaceae (incl. Hypolepidaceae, Monachosoraceae, Pteridiaceae) (10 genera, ca 240 species) * *Family Pteridaceae (incl. Acrostichaceae, Actiniopteridaceae, Adiantaceae, Anopteraceae, Antrophyaceae, Ceratopteridaceae, Cheilanthaceae, Cryptogrammaceae, Hemionitidaceae, Negripteridaceae, Parkeriaceae, Platyzomataceae, Sinopteridaceae, Taenitidaceae, Vittariaceae) (ca 44 genera, ca 1150 species) * *Family Aspleniaceae sensu lato (formerly eupolypods II, Blechnales, Athyriales, Aspleniales, or Thelypteridales) (ca 22 genera, ca 2780 species) * * *Subfamily Cystopteridoideae, formerly Cystopteridaceae * * *Subfamily Rhachidosoroideae, formerly Rhachidosoraceae * * *Subfamily Diplaziopsidoideae, formerly Diplaziopsidaceae * * *Subfamily Asplenioideae, formerly Aspleniaceae sensu stricto (incl. Hemidictyaceae) * * *Subfamily Thelypteridoideae, formerly Thelypteridaceae * * *Subfamily Woodsioideae, formerly Woodsiaceae * * *Subfamily Blechnoideae, formerly Blechnaceae (incl. Onocleaceae, Stenochlaenaceae) * * *Subfamily Athyrioideae, formerly Athyriaceae * *Family Polypodiaceae sensu lato (formerly eupolypods I * * *Subfamily Didymochlaenoideae * * *Subfamily Hypodematioideae, formerly Hypodematiaceae * * *Subfamily Dryopteridoideae, formerly Dryopteridaceae (incl. Aspidiaceae, Bolbitidaceae, Elaphoglossaceae, Peranemataceae) * * *Subfamily Lomariopsidoideae, formerly Lomariopsidaceae (incl. Nephrolepidaceae) * * *Subfamily Tectarioideae, formerly Tectariaceae * * *Subfamily Oleandroideae, formerly Oleandraceae * * *subfamily Davallioideae, formerly Davalliaceae * * *subfamily Polypodioideae sensu stricto, formerly Polypodiaceae sensu stricto (incl. Drynariaceae, Grammitidaceae, Gymnogrammitidaceae, Loxogrammaceae, Platyceriaceae, Pleurisoriopsidaceae) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Leptosporangiate fern」の詳細全文を読む スポンサード リンク
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