Warlock's Butter

Exidia pithya forms dark sepia to blackish, rubbery-gelatinous fruit bodies that are button-shaped at first and up to 5 centimetres (2 inches) across. The fruitbodies occur in groups and coalesce to form effused, irregular masses up to 30 cm (12 in) across. The upper, spore-bearing surface becomes irregularly folded, shiny, and dotted with small pimples or pegs. The individual fruitbodies are each attached to the wood at the base.

Microscopic characters. The microscopic characters are typical of the genus Exidia. The basidia are ellipsoid, septate, 11–20 × 8–12 μm. The spores are cylindrical, allantoid (sausage-shaped), 8–16.5 × 3–5.5 μm.

Similar species. On conifers, Exidia friesiana is very similar, but has a smooth surface without small pimples or pegs. On broadleaf trees, Exidia spiculata is similar, but also has a smooth surface. Exidia glandulosa and Exidia truncata are frequently confused with E. pithya but produce discrete, top-shaped fruitbodies that rarely if ever coalesce.

Exidia pithya is a wood-rotting species, typically found on dead attached branches of a wide range of broadleaf trees and, less frequently, conifers. It persists for some while on fallen branches and logs. It is widely distributed in Europe, but its presence in North America is uncertain.

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