fern
The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...
genus in the
Parkerioideae
Parkerioideae, synonym Ceratopteridoideae, is one of the five subfamilies in the fern family Pteridaceae. It includes only the two genera '' Acrostichum'' and ''Ceratopteris
''Ceratopteris'' is the only genus among homosporous ferns that is ...
subfamily of the
Pteridaceae
Pteridaceae is a family of ferns in the order Polypodiales, including some 1150 known species in ca 45 genera (depending on taxonomic opinions), divided over five subfamilies. The family includes four groups of genera that are sometimes recogni ...
. It was one of the original
pteridophyte
A pteridophyte is a vascular plant (with xylem and phloem) that reproduces by means of spores. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as " cryptogams", meaning that their means of reproduction is ...
genera delineated by
Linnaeus
Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...
. It was originally drawn very broadly, including all ferns that had sori apparently "acrostichoid", or distributed in a uniform mass across the back of the frond, rather than organized in discrete sori. This led Linnaeus to include such species as ''
Asplenium platyneuron
''Asplenium platyneuron'' (syn. ''Asplenium ebeneum''), commonly known as ebony spleenwort or brownstem spleenwort, is a fern native to North America east of the Rocky Mountains. It takes its common name from its dark, reddish-brown, glossy sti ...
'' in the genus, because the specimen he received had sori so crowded that it appeared acrostichoid.
Since '' Acrostichum aureum'' is regarded as the type for the genus, it is now narrowly circumscribed only to the natural genus of three species, that are allied to the genus ''
Ceratopteris
''Ceratopteris'' is the only genus among homosporous ferns that is exclusively aquatic. It is pan-tropical and classified in the Parkerioideae subfamily of the family Pteridaceae.
Description
Erect aquatic or subaquatic ferns of moderate si ...
''. They are collectively known as the leather ferns or leather swamp ferns, genus members commonly being found in swamps. The species of ''Acrostichum'' are massive ferns, with fronds up to tall, that depend on a semi-aquatic existence. They do not withstand prolonged immersion, but require wet roots. The species ''Acrostichum aureum'' is known to have a high saltwater tolerance, growing in
mangrove
A mangrove is a shrub or tree that grows mainly in coastal saline water, saline or brackish water. Mangroves grow in an equatorial climate, typically along coastlines and tidal rivers. They have particular adaptations to take in extra oxygen a ...