Exidia glandulosa - Witches' Butter

Taxonomy

Phylum: Basidiomycota

Class: Tremellomycetes

Order: Auriculariales

Exidia glandulosa - often referred to as Black Witch's (or Witches') Butter, perhaps because of its butter-like consistency when wet and its sombre colour - occurs throughout the year on dead hardwood. An alternative theory for the origin of its common name is that it was thought to have the power to counteract witchcraft if the fungi were thrown on to a blazing fire.

In wet weather Exidia glandulosa turns black and jelly like; however, during prolongued dry spells it shrinks to a series of cone-shaped olive-brown crusts. The individual fruit bodies often coalesce into large blobs typically 5cm to 15cm long.

Tremella mesenterica - Yellow Brain

Tremella mesenterica (above), the Yellow Brain Fungus, is sometimes referred to as Witch's Butter - further justification for always including the scientific name when making a reference to a particular species of fungus.

Autumn and winter are the best times to look for this jelly fungus, which is of dubious edibility (and in any case is too insubstantial to be worth collecting for food).

Identification Guide

Size	Individual fruit bodies grown to between 1 and 2cm across.
Description	Shiny black when wet, turning olive brown and shrivelling to a warty crust during very dry weather; gelatinous.
Spores	White.
Odour/taste	Not distinctive.
Habitat	Mainly on dead and decaying hardwood - notable hazel, beech and oak - but very occasionally also on pine.
Season	Throughout the year but most prevalent in late autumn, winter and early spring.
Occurrence	Fairly frequent and widespread.
Similar species	Tremella mesenterica is yellow and has a brain-like structure.