Exidia thuretiana  (Lév.) Fr. - White Brain Fungus

Distribution - Taxonomic History - Etymology - Identification - Culinary Notes - Reference Sources

Exidia thuretiana - White Brain

Taxonomy

Phylum: Basidiomycota

Class: Tremellomycetes

Order: Auriculariales

Family: Auriculariaceae

Exidia thuretiana is a relatively rare (at least in Britain and Ireland) species of jelly fungus; it appears on rotting hardwood, and particularly beech. In dry weather this fungus shrinks and becomes quite hard. You will need wet weather to find this fungus: during dry spells it shrivels up almost completely to leave just a transparent rubbery patch on the host wood.

Autumn and winter are the best times to look for this species.

Exidia thuretiana, older fruitbodies

Distribution

Exidia thuretiana occurs throughout Britain and Ireland, but in most areas it is rather an uncommon find. This jelly fungus can be seen also in many countries on mainland Europe and in northern Africa.

Taxonomic history

The basionym of this species was established in 1848 by the French physician and mycologist Joseph-Henri Léveillé (1796 - 1870), who described this jelly fungus and gave it the binomial scientific name Tremella thuretiana. Then in 1874 Swedish mycologist Elias Magnus Fries transferred this species to the genus Exidia, and so its scientific name became Exidia thuretiana, which remains its generally-accepted name today. (It wasalso Fries who, in 1822, separated out the genus Exidia from what had previously been a much larger genus Tremella.)

Synonyms of Exidia thuretiana include Tremella thuretiana Lév., but this jelly fungus has also been described by various authors under a number of other binomials including Exidia albida, Tremella albida, Tremella cerebrina, and Tremella hyalina.

Etymology

Exidia, the generic name, means exuding or staining, and both seem appropriate because these jelly fungi do look like exudations when moist and like dark stains on wood when they dry out.

The specific epithet thuretiana honours Gustave Adolphe Thuret (1817 - 1875), a noted French botanist and founder of the Jardin botanique de la Villa Thuret. M. Thuret was also the owner of the Château de Rentilly, in the grounds whereof Exidia thuretiana was first collected.

Identification guide

Exidia thuretiana, closeup of fruitbody

Fruitbody

Pure white when wet, drying to almost invisible, the fruiting bodies are cushion shaped, becoming contorted with age and fusing with neighbouring fruiting bodies to form a large mass several cm across. Individual fruit bodies grow to between 0.2 and 1cm across. (Picture: Paul Machin)

 

Spores

Cylindrical to allantoid (sausage-shaped), smooth, 13-18 x 5.5-7µm; inamyloid.

Spore print

White.

Odour/taste

Not distinctive.

Habitat

Mainly on dead and decaying hardwood, particularly Beech and Ash.

Season

Late autumn and early winter in Britain and Ireland.

Similar species

Tremella mesenterica is usually yellow and has a brain-like structure, but it does also have a (rare) white form.

Culinary Notes

This jelly fungus is of dubious edibility, and in any case it is too insubstantial to be worth collecting for food. We therefore class it as being of no culinary value.

Reference Sources

Pat O'Reilly (2011) Fascinated by Fungi; First Nature

British Mycological Society (2010). English Names for Fungi

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 and (for basidiomycetes) on Kew's Checklist of the British & Irish Basidiomycota.