''Ptisana purpurascens'' is a large fern belonging to the botanical family

Marattiaceae Marattiaceae is the only family of extant (living) ferns in the order Marattiales. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), Marattiales is the only order in the subclass Marattiidae. The family has six genera and about ...

. It has a

globular A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of member ...

rhizome In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...

with

stipule In botany, a stipule is an outgrowth typically borne on both sides (sometimes on just one side) of the base of a leafstalk (the petiole). Stipules are considered part of the anatomy of the leaf of a typical flowering plant, although in many speci ...

-like fleshy outgrowths. The leaves are dark green, twice pinnate and up to 1 metre long. Every pinnule has up to six pairs of leaflets. The petioles are dark-purplish, hence the name 'purpurascens' meaning 'becoming purple'. The

sporangia A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cy ...

are fused in all ''Ptisana'' into a bivalvate

synangium A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cy ...

. Conservation plans have been proposed for ''Ptisana purpurascens'', an

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

of the distant

Ascension Island Ascension Island is an isolated volcanic island, 7°56′ south of the Equator in the South Atlantic Ocean. It is about from the coast of Africa and from the coast of South America. It is governed as part of the British Overseas Territory o ...

in the South Atlantic, where a single population remains on Green Mountain. While the mature plants are still present in large numbers, long-term threats to its survival exist in the form of competition with alien invasive species like introduced plants such as ''

Buddleja madagascariensis ''Buddleja madagascariensis'', the smokebush or Madagascan butterfly bush, is a species of flowering plant in the figwort family Scrophulariaceae. It is a substantial evergreen shrub with fragrant yellow flowers through autumn and winter. Descri ...

'' and grazing by sheep and rabbits. Successful reproduction is very rare, making the species highly endangered.

References

*Gray, A., Palembe, T., Stroud, S. 2005. The conservation of the endemic vascular flora of Ascension Island and threats from alien species. Oryx 39: 449–453

*See the ARKive site for additional informatio

Marattiidae Flora of Ascension Island Near threatened plants Ferns of the Americas Plants described in 1853 {{Ascension-stub