| Ptisana purpurascens | |
|---|---|
| Conservation status | |
| Scientific classification | |
| Kingdom: | Plantae |
| Division: | Pteridophyta |
| Class: | Marattiopsida |
| Order: | Marattiales |
| Family: | Marattiaceae |
| Genus: | Ptisana |
| Species: | P. purpurascens (de Vries) Murdock] |
| Binomial name | |
| Ptisana purpurascens |
|
Ptisana purpurascens is a large fern belonging to the botanical family Marattiaceae. It has a globular rhizome with stipule-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 are fused in all Ptisana into a bivalvate synangium.
Conservation plans have been proposed for Ptisana purpurascens, an endemic of the distant Ascension Island in the South Atlantic, where a single population remains on Green Mountain. This population is now believed to be more stable than previously feared, but long-term threats to its survival do exist, in the form of competition with alien invasive species like introduced plants such as Lantana camara and grazing by sheep.