Tremella mesenterica Retz. - Yellow Brain Fungus

Taxonomy

Phylum: Basidiomycota

Class: Tremellomycetes (insertae sedis)

Order: Tremellales

Tremella mesenterica, the Yellow Brain Fungus, is mainly seen in winter, when it grows on fallen branches of deciduous trees. In dry weather this fungus becomes a hard orange bracket.

Late summer and autumn are the best times to look for this species, which is inedible (and in any case is too insubstantial to be worth collecting for food).

Identification Guide

	You will need wet weather to find this fungus: during dry spells it shrivels up almost completely to leave just a thin rubbery patch on the host wood. Initially disc-like, the fruitbody soon develops contortions resembling the structure of a brain. Yellow Brain fungus grows on dead timber from all kinds of broad-leaf trees, but it is particularly common on fallen branches of birch.
Size	Individual fruit bodies grown to between 2 and 8cm across.
Description	Golden yellow when damp, turning orange and shrivelling to a tiny fraction of its former size during very dry weather; gelatinous; no distinctive smell or taste.
Spores	White.
Odour/taste	Not distinctive.
Habitat	On dead and decaying hardwood, especially birch, ash and hazel. Occasionally found also on decaying gorse wood.
Season	Throughout the year but most prevalent in late autumn and early winter.
Occurrence	Frequent and widespread.
Similar species	Tremella lutescens is cream when dry and sulphur yellow when wet. Tremella foliacea is brown and has a lobed structure.

Reference Sources

Fascinated by Fungi, Pat O'Reilly 2011

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.