Gymnopilus decipiens (W.G. Sm.) P.D. Orton

Phylum: Basidiomycota - Class: Agaricomycetes - Order: Agaricales - Family: Strophariaceae

Distribution - Taxonomic History - Etymology - Toxicity - Identification - Reference Sources

This small and rarely seen rustgill is found mainly on burnt wood and forest fire sites. There are many other very similar rustgills worldwide, and identification to species level is extremely difficult, requiring microscopic examination of spores and other features.

The easiest rustgill to identify is Gymnopilus junonius, the Spectacular Rustgill, which often grows on the trunks of ailing trees; it is the only orange Gymnopilus with a persistent stem ring.

Distribution

Very rare in Britain, where it has been formally recorded in England and near the border between England and Wales, this small rustgill mushroom has been reported occasionally from Scandinavia as well as parts of France and Italy..

Taxonomic history

Described in 1869 by British mycologist W G Smith, who named it Agaricus decipiens, this rare wood-rotting mushroom species was transferred to the genus Gymnopilus in 1960 by another British mycologist, Peter Darbishire Orton (1916-2005).

Synonyms of Gymnopilus decipiens include Agaricus decipiens W.G. Sm., and Flammula decipiens (W.G. Sm.) Sacc.

Etymology

Gymnopilus was proposed as a new genus name in 1879 by the Finnish mycologist Petter Adolf Karsten (1834 - 1917). The origin of this generic name is the prefix Gymn- meaning naked, and the suffix -pilus which means cap - hence naked or bald caps would normally be an expected feature of the mushrooms in this genus. The specific epithet decipiens means deceptive... and this certainly is a very deceptive little mushroom.

If I was pressed to create a common name for this very rare mushroom, it would be the Forest Fire Rustgill.

Toxicity

As many of the Gymnopilus fungi contain the toxin psilobin, it is advisable to treat Gymnopilus decipiens and the many other small rustgills as poisonous mushrooms. In any case, these fungi are extremely rare and should not be gathered.

Identification guide

Cap	1 to 3cm across; convex, flattening; scaly or fibrillose; orange.
Gills	Adnate; fairly distant; yellow, turning reddish-brown, often with rusty-brown spots.
Stem	1 to 2cm long and 3 to 5mm in dia.; light brown, lower half covered in white fibres.
	Spores Ellipsoidal to almond-shaped, 7.1-8.3 x 4-4.5µm. Spore print Rusty brown. Basidia Four-spored.
Odour/taste	Odour not significant; taste bitter.
Habitat & Ecological role	On burned wood and sites of forest fires.
Season	June to November in Britain.
Similar species	Gymnopilus junonius is larger and retains a stem ring; it occurs in woodland habitat, but unlike Gymnopilus decipiens it is seen more often on hardwood stumps and ailing trees, and not normally on burnt wood. Phaeolepiota aurea is a rare mushroom with a granulase cap and lower stem; its spores are light yellow-brown.

Reference Sources

Pat O'Reilly (2016). 2nd edition; First Nature.

Lincoff, G. and D. J. Mitchel. (1977). Toxic and Hallucinogenic Mushroom Poisoning. Van Nostrand Reinhold, New York.

Bresinsky A, Besl H. (1990). A Colour Atlas of Poisonous Fungi. Wolfe Publishing. ISBN 0-7234-1576-5.

Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008

Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Society's GB Checklist of Fungi.

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