Witch's Butter

Witch's butter is a jelly fungus of the family Auriculariaceae. Wikipedia says that witch's butter is the recommended English name in the United Kingdom, and that in North America it is called black witches' butter, black jelly roll or warty jelly fungus. The fruit bodies are rubbery and gelatinous, brownish grey to black, top-shaped and up to 5 cm across. They grow singly or in groups on dead attached branches of oak and other broadleaf trees, mostly in autumn, and shrink to a flat black crust when dried. Wikipedia says it rots wood, and that it loosens the bark of dying branches. It adds that one American field guide calls it inedible, though another reports it as edible. The only source read for this entry is Wikipedia: neither Cunningham nor Kynes has an entry for it, so no magical correspondence is recorded.