Marattia purpurascens
Encyclopedia
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 petiole
s 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.
Rhizome
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...
with stipule
Stipule
In botany, stipule is a term coined by Linnaeus which refers to outgrowths borne on either side of the base of a leafstalk...
-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 petiole
Petiole (botany)
In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...
s 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
Ascension Island
Ascension Island is an isolated volcanic island in the equatorial waters of the South Atlantic Ocean, around from the coast of Africa and from the coast of South America, which is roughly midway between the horn of South America and Africa...
in the South Atlantic, where a single population remains on Green Mountain
Green Mountain
Green Mountain is a common name for "The Peak", the highest point, on Ascension Island which has gained some fame for claims that it is one of very few large-scale artificial forests.-History and Vegetation:...
. 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
Lantana camara
Lantana camara, also known as Spanish Flag or West Indian Lantana, is a species of flowering plant in the verbena family, Verbenaceae, that is native to the American tropics. It has been introduced into other parts of the world as an ornamental plant and is considered an invasive species in many...
and grazing by sheep.
See also
- Ptisana salicina, a related plant from New ZealandNew ZealandNew 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...
. - Danaea kalevalaDanaea kalevalaDanaea kalevala is a species of fern belonging to the family Marattiaceae. It is endemic to rainforests of the Lesser Antilles islands in the Caribbean....
, a related plant from the Caribbean.