Pteridium aquilinum, also known as eagle fern, is a species of fern occurring in temperate and subtropical regions in both hemispheres. The extreme lightness of its spores has led to its global distribution.
Etymology
Common bracken was first described as Pteris aquilina by Carl Linnaeus, in Volume 2 of his Species Plantarum in 1753. The origin of the specific epithet derived from the Latinaquila "eagle". In the reprint of the Flora Suecica in 1755, Linnaeus explains that the name refers to the image of an eagle seen in the transverse section of the root. In spite of this, the opinion has been forwarded that the name pertains to the shape of the mature fronds appearing akin to an eagle's wing. However, medieval scholars, including Erasmus, thought the pattern of the fibres seen in a transverse section of the stipe resembled a double-headed eagle or oak tree.
Taxonomy
It was traditionally treated as the sole species in the genus Pteridium ; authorities have split and recognised up to 11 species in the genus, however. It was placed in the genus Pteridium by Friedrich Adalbert Maximilian Kuhn in 1879.
Description
Common bracken is a herbaceousperennial plant, deciduous in winter. The large, roughly triangular fronds are produced singly, arising upwards from an underground rhizome, and grow to 0.3–1 m tall; the main stem, or stipe, is up to 1 cm diameter at the base. It dies back to ground level in autumn.
Reproduction
Sporangia are formed in sori on the underside of the frond. They are arranged in narrow brown bands, and form spores over July, August and September.
Habitat
Bracken grows in pastures, deciduous and coniferous woodlands, and hillsides. It prefers acidic soils. An adaptable plant, bracken readily colonises disturbed areas. It can even be aggressive in countries where it is native, such as England, where it has invaded heather stands on the North Yorkshire moors. In Ireland, bracken is found in open woodland and sandy pastures.
Bracken is a widely eaten vegetable in Korea, Japan and parts of China. In Korea, bracken is known as gosari. It is soaked, parboiled, and stir-fried, and often eaten as a side dish. It is also a classic ingredient of bibimbap. In Japan, young bracken shoots are steamed, boiled, or cooked in soups. The shoots are also preserved in salt, sake, or miso. Bracken shoots have been used to produce beer in Siberia, and among indigenous peoples of North America. The rhizome can be ground into flour to make bread. In the Canary Islands, the rhizome was historically used to make a porridge called gofio. Bracken leaves are used in the Mediterranean region to filter sheep's milk, and to store freshly made ricotta cheese.
Pharmacology
P. aquilinum has been investigated for its anti-inflammatory and antioxidative properties.
Toxicity
The plant contains the carcinogenic compound ptaquiloside. High stomach cancer rates are found in Japan and North Wales, where the young stems are used as a vegetable, but it is unknown whether bracken plays any part at all. Consumption of ptaquiloside-contaminated milk is thought to contribute to human gastric cancer in the Andean states of Venezuela. The spores have also been implicated as carcinogens. However, ptaquiloside is water soluble, and is reduced by soaking bracken in cool water. Korean and Japanese cooks have traditionally soaked the shoots in water and ash to detoxify the plant before eating. Ptaquiloside also degenerates at room temperature, which explains why the rat studies were done with the toxin stored at. At boiling temperature, the carcinogen denatures almost completely. Salt and baking soda also help with volatilizing the chemical. It has been suggested that selenium supplementation can prevent as well as reverse the immunotoxic effects induced by ptaquiloside from Pteridium aquilinum.
