Filmy fern
Encyclopedia
The Hymenophyllaceae is a family of seven genera and over 600 species of fern
s, with a subcosmopolitan
distribution, but generally restricted to very damp places or to locations where they are wetted by spray from waterfall
s or springs. A recent fossil find shows that ferns of Hymenophyllaceae have existed since at least the Upper Triassic.
The great majority of the species are found in tropical rainforest
s, 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 to the humid eastern third of the continent.
They often appear as very dark green or even black clumps and may be mistaken for a robust moss
or liverwort
. The stem is thin and wiry and the fronds variously pinnate with a single strand ("nerve") of vascular tissue
. In most species, the frond, apart from the vascular tissue, is only a single cell thickness, and they do not have any stoma
ta; this makes the plants very susceptible to desiccation
where a reliable water supply is not present. The sori
are borne at the leaf margins at the end of the nerve. Individual plants may persist for many years.
, but some older authorities (e.g. Copeland 1947) split the family up into as many as 34 different genera; several of these old genera are still accepted as subgenera (Flora of New Zealand 2004).
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
s, with a subcosmopolitan
Cosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...
distribution, but generally restricted to very damp places or to locations where they are wetted by spray from waterfall
Waterfall
A waterfall is a place where flowing water rapidly drops in elevation as it flows over a steep region or a cliff.-Formation:Waterfalls are commonly formed when a river is young. At these times the channel is often narrow and deep. When the river courses over resistant bedrock, erosion happens...
s or springs. A recent fossil find shows that ferns of Hymenophyllaceae have existed since at least the Upper Triassic.
The great majority of the species are found in tropical rainforest
Tropical rainforest
A tropical rainforest is an ecosystem type that occurs roughly within the latitudes 28 degrees north or south of the equator . This ecosystem experiences high average temperatures and a significant amount of rainfall...
s, but some also occur in temperate rainforests (particularly New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, with 25 species) and slightly drier forest regions. In Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
they are restricted to the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
fringes of the continent, notably in the Azores
Azores
The Archipelago of the Azores is composed of nine volcanic islands situated in the middle of the North Atlantic Ocean, and is located about west from Lisbon and about east from the east coast of North America. The islands, and their economic exclusion zone, form the Autonomous Region of the...
, Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
, and western Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
, but one species (Hymenophyllum tunbrigense) locally east to Luxembourg
Luxembourg
Luxembourg , officially the Grand Duchy of Luxembourg , is a landlocked country in western Europe, bordered by Belgium, France, and Germany. It has two principal regions: the Oesling in the North as part of the Ardennes massif, and the Gutland in the south...
, another (H. wilsonii) so far north as West Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
, Faeroes and South Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
, while in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, they are restricted to the humid eastern third of the continent.
They often appear as very dark green or even black clumps and may be mistaken for a robust moss
Moss
Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...
or liverwort
Marchantiophyta
The Marchantiophyta are a division of bryophyte plants commonly referred to as hepatics or liverworts. Like other bryophytes, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of genetic information....
. The stem is thin and wiry and the fronds variously pinnate with a single strand ("nerve") of vascular tissue
Vascular tissue
Vascular tissue is a complex conducting tissue, formed of more than one cell type, found in vascular plants. The primary components of vascular tissue are the xylem and phloem. These two tissues transport fluid and nutrients internally. There are also two meristems associated with vascular tissue:...
. In most species, the frond, apart from the vascular tissue, is only a single cell thickness, and they do not have any stoma
Stoma
In botany, a stoma is a pore, found in the leaf and stem epidermis that is used forgas exchange. The pore is bordered by a pair of specialized parenchyma cells known as guard cells that are responsible for regulating the size of the opening...
ta; this makes the plants very susceptible to desiccation
Desiccation
Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic substance that induces or sustains such a state in its local vicinity in a moderately sealed container.-Science:...
where a reliable water supply is not present. The sori
Sorus
A sorus is a cluster of sporangia .In fungi and lichens, the sorus is surrounded by an external layer. In some red algae it may take the form of a depression into the thallus....
are borne at the leaf margins at the end of the nerve. Individual plants may persist for many years.
Genera
Seven genera are accepted by the Germplasm Resources Information NetworkGermplasm Resources Information Network
Germplasm Resources Information Network or GRIN is an online software project of National Genetic Resources Program of USDA to provide germplasm information about plants, animals, microbes and invertebrates.-Sub-Projects:...
, but some older authorities (e.g. Copeland 1947) split the family up into as many as 34 different genera; several of these old genera are still accepted as subgenera (Flora of New Zealand 2004).
- Cardiomanes C.Presl
- Cephalomanes C. Presl
- CrepidomanesCrepidomanesCrepidomanes is a genus of ferns in the family Hymenophyllaceae.Species include:*Crepidomanes aphlebioides Bostock*Crepidomanes barnardianum Tindale*Crepidomanes bipunctatum Copel....
C. Presl - Hymenoglossum C. Presl
- HymenophyllumHymenophyllumHymenophyllum is a genus of ferns in the family Hymenophyllaceae. Its name means "membraneous leaf", referring to the very thin translucent tissue of the fronds, which gives rise to the common name filmy fern for this and other thin-leaved ferns. The leaves are generally only one cell thick and...
Sm. - Serpyllopsis Bosch
- TrichomanesTrichomanesTrichomanes is a large genus of ferns in the family Hymenophyllaceae, termed bristle ferns. Some botanists place it in its own family, Trichomanaceae. All ferns in the hymenophylloid clade are filmy ferns, with leaf tissue typically 2 cells thick...
L.