Exidia nigricans
| Exidia nigricans | |
|---|---|
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| Exidia nigricans | |
| Scientific classification | |
| Kingdom: | Fungi |
| Division: | Basidiomycota |
| Class: | Agaricomycetes |
| Order: | Auriculariales |
| Family: | Auriculariaceae |
| Genus: | Exidia |
| Species: | E. nigricans |
| Binomial name | |
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Exidia nigricans (With.) P. Roberts (2009) |
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| Synonyms | |
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Exidia applanata Schwein. (1832) |
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Exidia applanata Schwein. (1832)
Exidia plana Donk (1966)
Exidia nigricans (common name Witches' butter) is a jelly fungus in the family Auriculariaceae. It is a common, wood-rotting species throughout the northern hemisphere, typically growing on dead attached branches of broadleaf trees. It has been much confused with Exidia glandulosa.
The species was originally described from England as Tremella nigricans by Withering in 1776, based on a phrase name published by Dillenius in 1741. It was subsequently considered a synonym of Exidia glandulosa, until Donk revised species concepts in 1966 and placed it in synonymy with Exidia plana. Changes in the starting point for fungal nomenclature has made Exidia plana illegitimate, however, leaving Exidia nigricans as the earliest name for the species.
Molecular research has shown that Exidia glandulosa and E. nigricans, though similar, are distinct.
Both Dillenius (1741) and Withering (1776) gave the English name for this species as "Witches' butter", though this name has subsequently also been applied to other gelatinous fungi, including Exidia glandulosa and the yellow Tremella mesenterica. It is said to be based on a folk belief that witches milk cows at night and scatter the butter around. Clearly the butter they produce does not look appetizing. In Sweden, it is apparently known as "Troll smör" ("Troll's butter") for the same reason.
Exidia nigricans forms dark sepia to blackish, rubbery-gelatinous fruit bodies that are button-shaped and around 2 cm (0.79 in) across. The fruitbodies occur in clusters and quickly coalesce to form effused, irregular masses 10 cm (3.9 in) or more across. The upper, spore-bearing surface is shiny and dotted with small pimples or pegs. The individual fruitbodies are each attached to the wood at the base. The spore print is white.
The microscopic characters are typical of the genus Exidia. The basidia are ellipsoid, septate, 15-25 × 8-13 µm. The spores are allantoid (sausage-shaped), 14-19 × 4.5-5.5 µm.
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