Alsophila (plant)
Alsophila is a genus of tree ferns in the family Cyatheaceae.[1] It has also been considered to be a section in the subgenus Cyathea of the genus Cyathea.
Species of Alsophila have a treelike growth habit, with an erect trunk that rarely branches, or sometimes a more shrublike habit, with a creeping stem. Their fronds are large, with a strawlike stalk (stipe), dark brown or black in colour. Brown or dark brown scales are present, with distinct margins. The blade (lamina) of the frond is divided one to three times (one- to three-pinnate). The sori (spore-producing structures) are rounded and borne on smaller veins on the lower surface of the frond. An indusium (a covering to the sori) may or may not be present; if present initially, it may be lost as the frond ages.[2]
Alsophila is now separated from the other genera in the family Cyatheaceae primarily on the basis of molecular phylogenetic studies.[1] The scales on the stalks (petioles) provide a morphological distinction. Alsophila has scales with distinct margins, unlike Sphaeropteris, and with an apical hair or spine (seta), unlike Cyathea. The ornamentation of the spores also distinguishes Alsophila and Cyathea.[3][4]
The genus Alsophila was erected by Robert Brown in 1810.[5] It is placed in the family Cyatheaceae.[1] The division of the family into genera has had a long and controversial history.[4] Three or four clades have been suggested based on molecular phylogenetic studies. The Pteridophyte Phylogeny Group classification of 2016 (PPG I) accepts three genera, placing the Gymnosphaera clade within Alsophila.[1] In 2018, Dong and Zuo proposed the relationship shown in the cladogram below, and provided names in Gymnosphaera for species they considered to belong in this genus.[6]
Older sources, such as the New Zealand Organisms Register as of October 2000[update] and Large and Braggins (2004), place Alsophila within a broadly defined Cyathea.[7][8]
The Pteridophyte Phylogeny Group classification of 2016 (PPG I) accepted the genus Alsophila with 275 species.[1] As of July 2021[update], Plants of the World Online accepted 296 species.[9]
