Exidia glandulosa

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Exidia glandulosa
Exidia glandulosa 74739.jpg
Scientific classification
E. glandulosa
Binomial name
Exidia glandulosa
(Bull.) Fr. (1822)
  • Tremella arborea Huds. (1778)
  • Tremella atra O.F.Müll. (1782)
  • Tremella glandulosa Bull. (1789)
  • Tremella spiculosa Pers. (1796)
  • Exidia truncata Fr. (1822)

Exidia glandulosa (common names black witches' butter, black jelly roll, or warty jelly fungus) is a jelly fungus in the family Auriculariaceae. It is a common, wood-rotting species in Europe, typically growing on dead attached branches of oak. The 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.


The species was originally described from France as Tremella glandulosa by Bulliard in 1789.[1] It was subsequently placed in Exidia by Fries in 1822.[2] Fries, however, modified Bulliard's species concept to include a second, effused, coalescing species—the name Exidia glandulosa serving for both. This combined concept was used until Neuhoff separated the two species in 1936. Unfortunately, Neuhoff gave the name Exidia glandulosa to the effused species, adopting the name Exidia truncata for Bulliard's original species. This error was pointed out by Donk in 1966, who proposed the name Exidia plana for the effused species,[3] now replaced by Exidia nigricans.[4]

Molecular research has shown that Exidia glandulosa and E. nigricans, though similar, are distinct.[5]

The fungus is commonly known as "black witch's butter", "black jelly roll",[6] or the "warty jelly fungus".[7]


Exidia glandulosa forms dark sepia to blackish, rubbery-gelatinous fruit bodies that are top-shaped (like an inverted cone) and around 3 cm (1.2 in) across. They are firm when fresh, but become lax and distorted with age or in wet weather. The fruit bodies occur singly or in small clusters. The upper, spore-bearing surface is shiny and dotted with small pimples or pegs. The undersurface is smooth and matte at first, but develops a dense covering of small, gelatinous spines. The fruit bodies are attached to the wood at the base. The spore print is white.[8] When the fruit bodies are dried they can shrink to form a flattened black crust.[7]

Microscopic characters[edit]

The microscopic characters are typical of the genus Exidia. The basidia are ellipsoid, septate, 15–25 by 8–13 µm. The spores are allantoid (sausage-shaped), with dimensions of 14–19 by 4.5–5.5 µm.[8]

Spores of Exidia glandulosa

Similar species[edit]

Exidia nigricans
Bulgaria inquinans

Exidia glandulosa is frequently confused with Exidia nigricans. The two are similar, but E. nigricans produces button-shaped fruit bodies in clusters that quickly become deformed and coalesce, forming an effused, lobed mass that can be 10 cm (3.9 in) or more across. The two species are indistinguishable microscopically, but DNA research indicates they are distinct.[5] The closely related E. recisa has more erect fruit bodies without warts on the surface, lighter colors (ranging from yellowish brown to dark brown), and a small base.[7]

The ascomycete Bulgaria inquinans forms similar, rubbery-gelatinous, blackish fruit bodies on oak. Their upper surfaces are entirely smooth, however, and they produce copious black (not white) spore prints, often leaving a black stain if wiped with the hand.[9]

Habitat and distribution[edit]

Exidia glandulosa is a wood-rotting species, typically found on dead attached branches of broadleaf trees, especially oak, occasionally hazel or beech. It is a pioneer species capable of colonizing living or recently dead wood. A study of the wood decay process in attached oak branches showed that E. glandulosa is a member of a community of eight basidiomycetous fungi consistently associated with the decay of dying branches on living trees. Specifically, its role is to disintegrate the tissue of the vascular cambium, which loosens the attached bark.[10] It persists for some while on fallen branches and logs. Fruit bodies are normally produced in the autumn and winter. Its global distribution is uncertain because of confusion with E. nigricans, but it is present in Europe at least.


Exidia glandulosa is reported to be edible.[11]


  1. ^ Bulliard P. (1791). Histoire des champignons de la France. I (in French). Paris: l'auteur. p. 220. Retrieved 2010-03-13.
  2. ^ Fries EM. (1822). Systema Mycologicum (in Latin). 2. Lundae: Ex Officina Berlingiana. p. 224. Retrieved 2010-03-13.
  3. ^ Donk MA. (1966). "Check list of European hymenomycetous heterobasidiae". Persoonia. 4: 145–335.
  4. ^ Roberts P. (2009). "Exidia nigricans: a new and legitimate name for Exidia plana". Mycotaxon. 109: 219–20. doi:10.5248/109.219.
  5. ^ a b Weiss M, Oberwinkler F. (2001). "Phylogenetic relationships in Auriculariales and related groups – hypotheses derived from nuclear ribosomal DNA sequences". Mycological Research. 105 (4): 403–15. doi:10.1017/S095375620100363X.
  6. ^ Arora D. (1986). Mushrooms Demystified: a Comprehensive Guide to the Fleshy Fungi. Berkeley, California: Ten Speed Press. pp. 672–73. ISBN 0-89815-169-4. Retrieved 2010-03-13.
  7. ^ a b c McKnight VB, McKnight KH. (1987). A Field Guide to Mushrooms: North America. Boston: Houghton Mifflin. p. 66. ISBN 0-395-91090-0. Retrieved 2010-03-13.
  8. ^ a b Breitenbach J, Kranzlin F. (1985). Fungi of Switzerland: Non Gilled Fungi: Heterobasidiomycetes, Aphyllophorales, Gastromycetes. 2. Mad River Press. p. 66. ISBN 978-0-916422-67-7. (as E. truncata)
  9. ^ Breitenbach J, Kranzlin F. (1984). Fungi of Switzerland: A contribution to the knowledge of the fungal flora of Switzerland. 1. Verlag Mykologia. p. 156. ISBN 978-3-85604-205-9.
  10. ^ Boddy L, Rayner ADM. (1982). "Ecological roles of Basidiomycetes forming decay communities in attached oak branches". New Phytologist. 93 (1): 77–88. doi:10.1111/j.1469-8137.1983.tb02694.x. JSTOR 2431897.
  11. ^ Alan E. Besette [et al.] (2007). Mushrooms of the Southeastern United States. Syracuse University Press. p. 305. Retrieved 2014-01-19.

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