Hymenophyllaceae Temporal range: | |
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Hymenophyllum tunbrigense in Luxembourg | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Division: | Polypodiophyta |
Class: | Polypodiopsida |
Subclass: | Polypodiidae |
Order: | Hymenophyllales A.B.Frank |
Family: | Hymenophyllaceae Link |
Genera | |
See text |
The Hymenophyllaceae, the filmy ferns and bristle ferns, are a family of two to nine genera (depending on classification system) and about 650 known species [1] of ferns, with a subcosmopolitan distribution, but generally restricted to very damp places or to locations where they are wetted by spray from waterfalls or springs. Fossil evidence shows that ferns of the family Hymenophyllaceae have existed since at least the Upper Triassic. [2]
They often appear as very dark green or even black clumps and may be mistaken for a robust moss or liverwort. The rhizome is usually thin and wiry and the fronds variously pinnate with a single strand ("nerve") of vascular tissue. As in most ferns, young fronds have circinate vernation. In most species, the frond, apart from the vascular tissue, is only a single cell thick, and they do not have any stomata. The cuticle is also greatly reduced or absent, [3] leaving filmy ferns poikilohydric and very susceptible to desiccation where a reliable water supply is not present. [4] The leaves occasionally bear hairs, but scales are generally not present. [3] The sori are borne at the leaf margins [3] at the end of the nerve. They are protected by conical, bivalvate, or tubular indusia. Within the sori, sporangia mature starting at the apex of the sorus and progressing to the base. They have a continuous, oblique annulus and release round, green trilete spores. The spores grow into thread- or ribbon-like gametophytes; in many species, the gametophyte has an extended, independent lifespan and can reproduce asexually by fragmenting or releasing gemmae. [3]
Individual plants may persist for many years.
In the molecular phylogenetic classification of Smith et al. in 2006, the Hymenophyllales, containing the single family Hymenophyllaceae, were placed in class Polypodiopsida sensu stricto (the leptosporangiate ferns). [3] The linear sequence of Christenhusz et al. (2011), intended for compatibility with the classification of Chase and Reveal (2009) [5] which placed all land plants in Equisetopsida, [6] reclassified Smith's Polypodiopsida as subclass Polypodiidae and placed the Hymenophyllales there. The circumscription of the order and its families was not changed, [5] and that circumscription and placement in Polypodiidae has subsequently been followed in the classifications of Christenhusz and Chase (2014) [7] and PPG I (2016). [8]
The division of the family into genera was disputed, as of October 2019 [update] . Traditionally, only two genera of Hymenophyllaceae have been recognized: (1) Hymenophyllum with bivalved involucres, and (2) Trichomanes s.l. with tubular involucres. Subsequent proposals have created 34 genera (Copeland 1938), 6 genera (Morton 1968), 47 genera (Sermolli 1977), and 8 genera (Iwatsuki 1984). These classifications all had only limited regional acceptance. Recent molecular phylogenic studies do show two distinct monophyletic clades of fairly equal size, but they are only roughly aligned with the two traditional genera. For example, the traditional Trichomanes subtaxa Pleuromanes and Cardiomanes were shown to belong to the "hymenophylloid" clade. To reflect these recent discoveries Atsushi Ebihara and Kunio Iwatsuki, in 2006, revised the taxonomy of Hymenophyllaceae to place all species of the "hymenophylloid" clade in a single genus Hymenophyllum, and to place the eight clear "trichomanoid" subclades in eight corresponding genera. [9]
This subdivision was recognized by Smith et al. in 2006 [3] and Christenhusz et al. in 2011, [5] but Christenhusz and Chase, in 2014, reverted to combining the trichomanoid clades into Trichomanes. [7] The PPG I classification of 2016 again recognizes the segregate genera (and treats the two clades as subfamilies, Hymenophylloideae and Trichomanoideae), [8] although the segregate genera are not always accepted by contemporary floras; e.g., as of 2016, the Flora of New Zealand preferred to recognize Trichomanes s.l. due to the difficulty of morphologically distinguishing the segregate genera. [10]
The genera used in PPG I and the subgenera assigned by the system of Ebihara et al. are:
Phylogeny of Hymenophyllaceae [9] | |||||||||
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Phylogeny of Hymenophyllaceae [11] [12] | |||||||||||||||
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The great majority of the species are found in tropical rainforests, but some also occur in temperate rainforests (particularly New Zealand, with 25 species) and slightly drier forest regions. In Europe they are restricted to the Atlantic Ocean fringes of the continent, notably in the Azores, Ireland, and western Great Britain, but one species (Hymenophyllum tunbrigense) locally east to Luxembourg, another (H. wilsonii) so far north as West Norway, Faeroes and South Iceland, while in North America, they are restricted (often occurring solely as gametophytes) to the humid eastern third of the continent and the rainforests of the Pacific Northwest.
Ophioglossaceae, the adder's-tongue family, is a small family of ferns. In the Pteridophyte Phylogeny Group classification of 2016, it is the only family in the order Ophioglossales, which together with the Psilotales is placed in the subclass Ophioglossidae. The Ophioglossidae are one of the groups traditionally known as eusporangiate ferns. Members of the family differ from other ferns in a number of ways. Many have only a single fleshy leaf at a time. Their gametophytes are subterranean and rely on fungi for energy.
The Dryopteridaceae are a family of leptosporangiate ferns in the order Polypodiales. They are known colloquially as the wood ferns. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), the family is placed in the suborder Polypodiineae. Alternatively, it may be treated as the subfamily Dryopteridoideae of a very broadly defined family Polypodiaceae sensu lato.
A pteridophyte is a vascular plant 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 hidden.
Trichomanes is a genus of ferns in the family Hymenophyllaceae, termed bristle ferns. The circumscription of the genus is disputed. All ferns in the genus are filmy ferns, with leaf tissue typically 2 cells thick. This thinness generally necessitates a permanently humid habitat, and makes the fronds somewhat translucent. Because of this membrane-like frond tissue, the plant is prone to drying out. “Filmy ferns” in the taxa Hymenophyllaceae grow in constantly wet environments. Many are found in cloud forests such as “Choco” in Colombia. There are also members of the taxa that can grow submersed in water.
Polyphlebium tenuissimum, synonym Trichomanes tenuissimum, is a species of fern in the family Hymenophyllaceae. It is endemic to Ecuador. In 2006, in a taxonomic revision of the family Hymenophyllaceae, Ebihara et al. assigned this species to the genus Polyphlebium rather than Trichomanes. However the combination does not appear to have been formally published; hence the "comb. ined." in the Checklist of Ferns and Lycophytes of the World.
Crepidomanes intricatum, synonym Trichomanes intricatum, is known as the weft fern. The genus Crepidomanes is accepted in the Pteridophyte Phylogeny Group classification of 2016, but not by some other sources. As of October 2019, Plants of the World Online sank the genus into a broadly defined Trichomanes, treating this species as Trichomanes intricatum.
Hymenophyllum australe, commonly known as austral filmy fern, is a relatively large rupestral and epiphytic fern, indigenous to eastern Australia and New Zealand. It belongs to the unique Hymenophyllum genus, which are characterised by their thin membranous fronds that are seldom more than one cell thick, with the exception of regions over and around veins. Hymenophyllum australe is distinctive in that the fronds are typically thicker than other Hymenophyllum species, often being up to 2-3 cells thick.
Hymenophyllum flabellatum, the shiny filmy-fern, is a species of fern in the family Hymenophyllaceae. This delicate fern is commonly epiphytic and is between 5 and 25 cm in length. It is distinct, with its thin, one-celled thick, membranous leaves. It is from the family Hymenophyllaceae and is dispersed world wide. The species is dispersed highly throughout Tasmanian rainforests and in the south east of mainland Australia, with small pockets of the population seen in northern Queensland.
Matoniaceae is one of the three families of ferns in the Gleicheniales order of the Polypodiopsida class. Fossil records reveal that Matoniaceae ferns were abundant during the Mesozoic era, during which they lived on every continent, including Antarctica, with eight genera and 26 species, with the oldest known specimens being from the Middle Triassic of Antarctica. Today the family is much less abundant, and also less diverse, with only two extant genera and four species, which are limited to portions of southeastern Asia.
Didymoglossum is a tropical genus of ferns in the family Hymenophyllaceae. It comprises more than 30 epilithic or low-epiphytic species under two subgenera. The genus is accepted in the Pteridophyte Phylogeny Group classification of 2016, but not by some other sources which sink it into a broadly defined Trichomanes.
Cephalomanes is a fern genus in the family Hymenophyllaceae. The genus is accepted in the Pteridophyte Phylogeny Group classification of 2016 but not by other sources, which sink it into a broadly defined Trichomanes.
Hymenophyllum tunbrigense, the Tunbridge filmy fern or Tunbridge filmy-fern, is a small, fragile perennial leptosporangiate fern which forms large dense colonies of overlapping leaves from creeping rhizomes. The common name derives from the leaves which are very thin, only a single cell thick, and translucent, giving the appearance of a wet film. The evergreen fronds are bipinnatifid, deeply and irregularly dissected, about 3 to 6 cm long, 2 cm across with dark winged stipes. In contrast to the similar H. wilsonii the fronds are more divided, flattened, appressed to the substrate and tend to have a bluish tint.
Abrodictyum caudatum is an epiphytic fern, found in rainforests in eastern Australia.
Callistopteris is a fern genus in the family Hymenophyllaceae. The genus is accepted in the Pteridophyte Phylogeny Group classification of 2016 but not by some other sources, which sink it into a broadly defined Trichomanes.
Polyphlebium is a fern genus in the family Hymenophyllaceae. The genus is accepted in the Pteridophyte Phylogeny Group classification of 2016 but not by some other sources.
Vandenboschia is a fern genus in the family Hymenophyllaceae. The genus is accepted in the Pteridophyte Phylogeny Group classification of 2016 but not by some other sources.
Abrodictyum is a fern genus in the family Hymenophyllaceae. The genus is accepted in the Pteridophyte Phylogeny Group classification of 2016 but not by some other sources, which sink it into a broadly defined Trichomanes.
Cephalomanes atrovirens is a species of fern in the family Hymenophyllaceae. The genus Cephalomanes is accepted in the Pteridophyte Phylogeny Group classification of 2016, but not by some other sources. As of October 2019, Plants of the World Online sank the genus into a broadly defined Trichomanes, while treating the subtaxa of this species as the separate species Trichomanes acrosorum, Trichomanes atrovirens, Trichomanes boryanum and Trichomanes kingii.
Crepidomanes minutum is small fern in the filmy fern family which grows throughout the Pacific. It is commonly referred to as tiny bristle fern. The specific epithet 'minutum' means small in Latin, referring to the small fronds