''Rhizomarasmius undatus'' ( syn. ''

Marasmius ''Marasmius'' is a genus of mushroom-forming fungi in the family Marasmiaceae. It contains about 500 species of agarics, of which a few, such as '' Marasmius oreades'', are edible. However, most members of this genus are small, unimpressive ...

undatus'') is a small mushroom which grows on fern

rhizomes 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 ...

Description

The species can be described as follows: *The cap has a powdery covering (a pruina), is initially whitish and convex and later becomes brownish grey and expands to be flat. It grows to about 2.5 cm in diameter. *The gills are whitish and distant, and broadly

adnate Adnate may refer to: * Adnation, in botany, the fusion of two or more whorls of a flower * Adnate, in mycology, a classification of lamellae (gills) * Conjoined twins Conjoined twins – sometimes popularly referred to as Siamese twins – are ...

to the stem, or slightly decurrent. The spore powder is white. *The rigid stem can grow to about 12 cm long by about 2 mm in diameter. It is white at the top and dark brown to black lower down, with a puinose covering of short white hairs. *The smell and taste are not distinctive. *The spores are lemon-shaped to ellipsoid and measure roughly 9-12 µm x 5-7 µm.

Naming and related species

The species epithet ''undatus'', meaning "wavy", is the past participle of the Latin verb "undo" (= "I undulate"). This species was originally described in 1836 as ''Agaricus undatus'' by Miles Joseph Berkeley. As it happened, in 1838 the famous mycologist

Elias Magnus Fries Elias Magnus Fries (15 August 1794 – 8 February 1878) was a Swedish mycologist and botanist. Career Fries was born at Femsjö (Hylte Municipality), Småland, the son of the pastor there. He attended school in Växjö. He acquired ...

defined a completely different mushroom (now ''Entoloma undatum'') under the same name, but due to the nomenclatural rules of precedence, that definition is illegitimate. This was confirmed when in 1849 Fries renamed Berkeley's fungus with the combination ''Marasmius undatus'', a name which was current for more than a century. Then in 2000 it was one of the two initial species with which R. H. Petersen created the new genus ''

Rhizomarasmius ''Rhizomarasmius'' is a genus of fungi in the family Physalacriaceae, containing about five species. General The genus was created in 2000 by R. H. Petersen to accommodate two species then classified in Marasmius (''M. pyrrhocephalus'' and ''M. ...

'', the other one being the type species ''R. pyrrhocephalus''.

Ecology and distribution

This mushroom grows on

of bracken ( Pteridium aquilinum) and probably other ferns. It is widespread but rare in northern and western Europe and has been reported from North Africa, North America, and the

Altai mountains The Altai Mountains (), also spelled Altay Mountains, are a mountain range in Central Asia, Central and East Asia, where Russia, China, Mongolia and Kazakhstan converge, and where the rivers Irtysh and Ob River, Ob have their headwaters. The m ...

References

{{Taxonbar, from=Q10436915 undatus Fungi of Europe