Stangeria eriopus is a cycad endemic to southern Africa. It is the sole species in the genus Stangeria.

Description

Stangeria eriopus is a very long-lived, perennial, evergreen cycad. The stalked, feathered, fern-like leaves are between 25 centimeters and two meters long, with the petiole comprising one third to one half of the overall length (in both varieties). They are pinnately-veined, which distinguishes the species from all other cycads. The petiole comprises half the length of the leaf. The young leaves are bent in bud position, the tip appears rolled up. Young leaves are dotted with short, gray hairs (trichomes), which usually fall off quickly and only stick to the petiole. These trichomes are unbranched and transparent or colored. The species occurs as two variable forms or varieties. The forest form, growing in regions with higher rainfall, is characterized by large, wide leaves that can reach up to 2 m in length. The grassland form, growing in regions subject to annual fire and drought, has shorter leaves with a thicker cuticle that may only be 30 cm long.

Tubers

thumb|left|Underground tuber stem

Stems are completely subterranean and the root tuber is shaped like a carrot, which reaches a diameter of 10 to 25 centimeters. The tip bifurcates into several shoot tips. These form at the beginning wooly scales, but fall off early. As in other cycads, S. eriopus forms coralloid roots. These are specialized, plagiotropic (sideways-growing) roots housing colonies of cyanobacteria Bacillus radicola and Azotobacter sp. that fix nitrogen, much like the roots of legumes.

The tuber is rich in carbohydrates and contains an exceptionally high concentration of sodium sulfate, which explains the breaking-irritant effect. The most common biflavones in the leaves are amentoflavone and bilobetin.

Discovery

When Gustav Kunze discovered the first plants, he incorrectly designated them as ferns probably due to the primitive nerves, under the name Lomaria coriacea. In 1839 he described it again as a separate species of fern as Lomaria eriopus. It was not until 1851 that William Stanger discovered that they were cycads when he observed the cones. He sent samples to England, where they were described by Thomas Moore described the Art 1853 as Stangeria paradoxa and thus also established the genus. However, since the epithet "eriopus" of Kunze was validly described, Henri Ernest Baillon with his description in 1892 the correct name as Stangeria eriopus.

Etymology

The genus was named in honor of William Stanger (1811-1854), who sent the first cones to England. He was an English physician and naturalist who worked in South Africa.

The binomial name comes from the Greek prefix erio-, meaning "woolly", and suffix -pus, "footed", referring to the woolly petiole bases. It was named in honour of William Stanger, a former surveyor-general of Natal. Common names includes Natal grass cycad, Hottentot's head and Stangeria.

Cytology

The species has 2n = 16 chromosomes. The cladogram shows twelve metacentric, two submetacentric and two acrocentric chromosomes.

Systematics and Taxonomy

The closest relative to Stangeria eriopus was thought to be the genus Bowenia, both placed in the family Stangeriaceae. Another candidate is the extinct Tertiary genus Eostangeria.

However, molecular phylogenetic studies show that Stangeria is more closely related to the genus Ceratozamia or to Zamia and Microcycas than to Bowenia, implying that the Stangeriaceae are not a monophyletic group.

Uses

In South African traditional medicine, the thickened subterranean tuber stem serves both for the production of various magical tinctures and as an emetic. The dried tuber is also mixed with feed to combat internal parasites in cattle.

For these purposes, the plants are collected and sold, this goes so far that the stock is now endangered. For one gram of tuber, 5 cents were paid on the market in Mthala in 2005.

References

Bibliography

  • The Cycad Pages: Stangeria eriopus
  • Cycad Society of South Africa: Stangeria eriopus