Exidia glandulosa

Exidia glandulosa is a species of fungus in the family Auriculariaceae. In the UK, it has the recommended English name of witch's butter. In North America it has variously been called black witches' butter, black jelly roll, or warty jelly fungus. It is a common, wood-rotting species in Europe, typically growing on dead attached branches of oak. The gelatinous basidiocarps (fruit bodies) are up to 3 cm (1.2 in) wide, shiny, black and blister-like, and grow singly or in clusters. Its occurrence elsewhere is uncertain because of confusion with the related species, Exidia nigricans.