Gleicheniaceae

Forked ferns
Diplopterygium pinnatum of the Gleichenioideae
Scientific classification
Kingdom:	Plantae
Division:	Pteridophyta (but see text)
Class:	Polypodiopsida /  Pteridopsida (disputed)
Order:	Gleicheniales (but see text)
Family:	Gleicheniaceae (R.Br.) C.Presl
Subfamilies
Gleichenioideae Stromatopteridaeae
Synonyms
Dicranopteridaceae Stromatopteridaceae Stromatopteridales

The forked ferns are the family Gleicheniaceae. They are sometimes – like all ferns – placed in an infradivision Monilophytes of subdivision Euphyllophytina, allowing for more precise phylogenetic arrangement of the tracheophytes. More conventionally, the name Pteridophyta, ranked as a division, is used in lieu of the Monilophytes. The formerly independent families Dicranopteridaceae and Stromatopteridaceae are nowadays generally included in the Gleicheniaceae, whereas the Dipteridaceae and Matoniaceae, though closely related, are considered spearate families by most authors.^[1]

These tropical ferns are the most widespread living lineage of Gleicheniales. Their rhizomes have a "vitalized" protostele or in some taxa a solenostele. The leaves are indeterminate, with pseudodichotomously forked leaves except in Stromatopteris, and free veins. The sori are abaxial but not marginal and carry 5–15 exindusiate round sporangia each. These have a transverse-oblique annulus and contain 128 to 800 bilateral or globose-tetrahedral spores. The sori and sporangia mature at the same time, and the spores grow into surface-dwelling green prothalliums beset with club-shaped hairs.^[1]

Systematics

There is some dispute about ranking these ferns. They are typically placed in the order Gleicheniales. This is alternatively be considered a subclass Gleicheniatae or class Gleichenopsida, so that a distinct taxon can be established for the leptosporangiate ferns. In this case, the Gleicheniaceae are upranked to an order and receive the name Gleicheniales. Irrespective of their modern taxonomic treatment, the Gleicheniaceae were formerly included in the order Polypodiales. But the ferns in the loose sense are much too diverse a group to be shoehorned into one taxon at such a low rank.^[1]

The Triassic Antarctipteris and Gleichenipteris are sometimes ascribed to the Gleicheniaceae, but are probably better considered Gleicheniales incertae sedis.^[1] The two living subfamilies contain six genera:

Subfamily Gleichenioideae

• Dicranopteris
• Diplopterygium
• Gleichenella
• Gleichenia
• Sticherus

Subfamily Stromatopteridaeae

• Stromatopteris

Footnotes

References

• A. R. Smith, A. R. Kathleen, M. Pryer, E. Schuettpelz, P. Korall, H. Schneider & P. G. Wolf. 2006. A classification for extant ferns. Taxon 55(3): 705–731. PDF fulltext
• C. Michael Hogan. 2010. Fern. Encyclopedia of Earth. eds. Saikat Basu and C. Cleveland. National Council for Science and the Environment. Washington, D.C.

External links

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