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The tree ferns are arborescent (tree-like) ferns that grow with a trunk elevating the fronds above ground level, making them trees. Many extant tree ferns are members of the order Cyatheales, to which belong the families Cyatheaceae (scaly tree ferns), Dicksoniaceae, Metaxyaceae, and Cibotiaceae. It is estimated that Cyatheales originated in the early Jurassic, [1] [2] and is the third group of ferns known to have given rise to tree-like forms. The others are the extinct Tempskya of uncertain position, [3] and Osmundales where the extinct Guaireaceae and some members of Osmundaceae also grew into trees. In addition there were the Psaroniaceae and Tietea in the Marattiales, which is the sister group to most living ferns including Cyatheales.
Other ferns which are also tree ferns, are Leptopteris and Todea in the family Osmundaceae, which can achieve short trunks under a metre tall. Fern species with short trunks in the genera Blechnum , Cystodium and Sadleria from the order Polypodiales, and smaller members of Cyatheales like Calochlaena , Cnemedaria , Culcita (mountains only tree fern), Lophosoria and Thyrsopteris are also considered tree ferns.
Tree ferns are found growing in tropical and subtropical areas worldwide, as well as cool to temperate rainforests in Australia, New Zealand and neighbouring regions (e.g. Lord Howe Island, etc.). Like all ferns, tree ferns reproduce by means of spores formed on the undersides of the fronds.
The fronds of tree ferns are usually very large and multiple-pinnate. Their trunk is actually a vertical and modified rhizome, [4] and woody tissue is absent. To add strength, there are deposits of lignin in the cell walls and the lower part of the stem is reinforced with thick, interlocking mats of tiny roots. [5] If the crown of Dicksonia antarctica (the most common species in gardens) is damaged, it will inevitably die because that is where all the new growth occurs. But other clump-forming tree fern species, such as D. squarrosa and D. youngiae, can regenerate from basal offsets or from "pups" emerging along the surviving trunk length. Tree ferns often fall over in the wild, yet manage to re-root from this new prostrate position and begin new vertical growth.
This section is largely based on an article in the out-of-copyright Encyclopædia Britannica Eleventh Edition, which was produced in 1911.(May 2021) |
Tree-ferns have been cultivated for their beauty alone; a few, however, were of some economic application, chiefly as sources of starch. These include the Sphaeropteris excelsa of Norfolk Island that was threatened with extinction for the sake of its sago-like pith, which was eaten by pigs. It is now widely cultivated as an ornamental tree, although there is only one small wild population on Norfolk Island. [6] Sphaeropteris medullaris (mamaku, black tree fern) also furnished a kind of sago to people living in New Zealand, Queensland and the Pacific islands. A Javanese species of Dicksonia (D. chrysotricha) furnishes silky hairs, which were once imported as a styptic, and the long silky or wooly hairs, abundant on the stem and frond-leaves in the various species of Cibotium have not only been put to a similar use, but in the Hawaiian Islands furnished wool for stuffing mattresses and cushions, which was formerly an article of export. [7]
It is not certain the exact number of species of tree ferns there are, but it may be close to 600-700 species. [8] Many species have become extinct in the last century as forest habitats have come under pressure from human intervention.[ citation needed ]
The order Cyatheales, which includes most tree ferns, is a taxonomic order of the fern class, Polypodiopsida. No clear morphological features characterize all of the Cyatheales, but DNA sequence data indicate the order is monophyletic. Some species in the Cyatheales have tree-like growth forms from a vertical rhizome, others have shorter or horizontal expanding rhizomes.
Dicksonia is a genus of tree ferns in the order Cyatheales. It is regarded as related to Cyathea, but is considered to retain more primitive traits, dating back at least to the Jurassic and Cretaceous periods. The fossil record includes stems, pinnules, and spores.
Cibotium, also known as manfern, is a genus of 11 species of tropical tree ferns. It is the only genus in family Cibotiaceae in the Pteridophyte Phylogeny Group classification of 2016. Alternatively, the family may be treated as the subfamily Cibotioideae of a very broadly defined family Cyatheaceae, the family placement used for the genus in Plants of the World Online as of November 2019.
Dicksonia antarctica, the soft tree fern or man fern, is a species of evergreen tree fern native to eastern Australia, ranging from south-east Queensland, coastal New South Wales and Victoria to Tasmania.
Sphaeropteris cooperi, synonym Cyathea cooperi, also known as lacy tree fern, scaly tree fern, or Cooper's tree fern, is a tree fern native to Australia, in New South Wales and Queensland.
The Cyatheaceae are a family of ferns, the scaly tree ferns, one of eight families in the order Cyatheales in the Pteridophyte Phylogeny Group classification of 2016. Alternatively, the family may defined much more broadly as the only family in the Cyatheales, with the PPG I family treated as the subfamily Cyatheoideae. The narrower circumscription is used in this article.
Dicksoniaceae is a group of tropical, subtropical and warm temperate ferns, treated as a family in the Pteridophyte Phylogeny Group classification of 2016, and counting 30-40 species. Alternatively, the family may be sunk into a very broadly defined family Cyatheaceae sensu lato as the subfamily Dicksonioideae. Most of the genera in the family are terrestrial ferns or have very short trunks compared to tree ferns of the family Cyatheaceae sensu stricto. However, some of the larger species can reach several metres in height. A number of others are epiphytes. They are found mostly in tropical regions in the Southern Hemisphere, as far south as southern New Zealand. Larger tree ferns in the genus Cibotium were formerly included in Dicksoniaceae, but are now segregated as the family Cibotiaceae.
Thyrsopteris is a genus of tree fern. It contains a single living species, Thyrsopteris elegans, endemic to the Juan Fernandez Archipelago off the coast of Chile. Thyrsopteris is the only genus in the family Thyrsopteridaceae in the Pteridophyte Phylogeny Group classification of 2016. Alternatively, the genus may be placed in the subfamily Thyrsopteridoideae of a more broadly defined family Cyatheaceae, the family placement used in Plants of the World Online as of November 2019. The oldest records of the genus are the species Thyrsopteris cretacea and Thyrsopteris cyathindusia which were described from the Burmese amber of Myanmar, dating to the Cenomanian of the Cretaceous period, around 99 million years ago. Other fossil species include Thyrsopteris antiqua from the Upper Cretaceous of Chile and Thyrsopteris shenii from the Paleogene of King George Island, Antarctica A thyrsopterid rachis is also known from the Upper Cretaceous of Japan.
Sphaeropteris medullaris, synonym Cyathea medullaris, commonly known as mamaku or black tree fern, is a large tree fern up to 20 m tall. It is distributed across the south-west Pacific from Fiji to Pitcairn Island. Its other Māori names include katātā, kōrau, or pītau.
Sphaeropteris excelsa, synonym Cyathea brownii, commonly known as the Norfolk tree fern or smooth tree fern, is probably the largest fern species in the world. It is endemic to Norfolk Island, in the Pacific Ocean near Australia and New Zealand. It is named after the botanist Robert Brown (1773-1858).
Sphaeropteris is a genus of tree fern in the family Cyatheaceae. It has been treated as a subgenus within the genus Cyathea, but is accepted in the Pteridophyte Phylogeny Group classification of 2016.
Alsophila australis, synonym Cyathea australis, also known as the rough tree fern, is a species of tree fern native to southeastern Queensland, New South Wales and southern Victoria in Australia, as well as Tasmania and Norfolk Island.
Alsophila hermannii, synonym Cyathea christiiCopel., is a species of tree fern endemic to Mindanao in the Philippines, where it grows in forest at an altitude of 900–1800 m. The trunk is erect and may be 5 m tall or more. Fronds are bi- or tripinnate and 2–3 m long. The stipe is covered with some warts and narrow, brown scales. Sori occur near the midvein of fertile pinnules and are covered by thin, fragile indusia.
Alsophila glaucifolia, synonym Cyathea glauca, is a species of tree fern endemic to Réunion. Little is known about this species.
Cibotium menziesii, the hāpuʻu ʻiʻi or Hawaiian tree fern, is a species of tree fern that is endemic to the islands of Hawaiʻi. It is named after the Scottish naturalist Archibald Menzies. It is also known as the male tree fern, and Cibotium glaucum is deemed the female tree fern due to differences in color.
Lophosoria quadripinnata(J.F.Gmel.) C.Chr. is a species of fern that, according to DNA molecular analysis, belongs to the family Dicksoniaceae, where it is placed in the genus Lophosoria. It is found in the Americas spanning from Cuba and Mexico to Chile. In Chile it is present in the area between Talca and Aysén including Juan Fernández Islands. In Argentina it grows only in the humid valleys of western Neuquén and Río Negro Province. Diamondleaf fern is a common name. In Spanish it is known as 'ampe' or palmilla, but one has to remember that there are several species of ferns called "palmillas" that have larger or smaller fronds, and which grow in colder climates. It is a medium-sized plant, growing to about 4–5 feet and even though the rhizome does not grow a trunk, it is clearly related to the other tree ferns due to features that were apparently already present in their common ancestor, like 'pneumathodes', and the rhizome which changed from the dorsiventral symmetry typical of the other ferns, to a radial symmetry typical of tree ferns. Their large and multiple pinnate fronds, with the petiole raised adaxially, and the hairs on the rhizome and lower part of the petioles, also resemble those of tree ferns. To identify the species, use the position and characteristics of the spores found on the fertile fronds. The genus already existed in the Cretaceous Period in southern Gondwana according to fossil remains found in Antarctica. The species is well known as an ornamental plant.
Sphaeropteris australis, synonyms Alsophila leichhardtiana and Cyathea leichhardtiana, the prickly tree fern, is a plant in the tree fern family, Cyatheaceae. It is native to eastern Australia. It is a common species found in moist situations, in and near rainforests.
Metaxya is a neotropical genus of ferns in the order Cyatheales. It is the only genus in the family Metaxyaceae in the Pteridophyte Phylogeny Group classification of 2016. Alternatively, the genus may be placed in the subfamily Metaxyoideae of a more broadly defined family Cyatheaceae, the family placement used in Plants of the World Online as of November 2019.
Alsophila borbonica, synonym Cyathea borbonica, is a tree fern endemic to Mauritius and Réunion. There are several natural forms and varieties.
Cyathea arborea is a plant of the family Cyatheaceae in the order Cyatheales.