Exidia glandulosa
Description
Exidia glandulosa is a type of fungus found in Europe that grows on dead branches of oak trees. It produces shiny black blister-like fruit bodies that can be up to 3 cm wide, and grow alone or in groups. The fruit bodies are initially firm but can become soft and distorted with age or in wet weather. The top surface is shiny and dotted with small bumps while the underside is smooth at first but later develops small spines. The fungus causes white rot in the wood, breaking down the lignin. When the fruit bodies dry out, they can shrink to form a flat black crust.
In wet weather, Exidia glandulosa turns black and jelly-like; however, during prolonged dry spells, it shrinks to a series of cone-shaped olive-brown crusts. The individual fruit bodies sometimes coalesce to form larger blobs.
According to research by Rockett TR and Kramer CL (1974) in Mycologia 66:926-941, the fungus can produce 6,500 spores per hour per square centimeter over a three-month period.
Common names: Black Witches Butter, Black Jelly Roll, Warty Jelly Fungus, German (Abgestutzter Drüsling, Stoppeliger Drüslinge), Netherlands (Eikentrilzwam).
Mushroom Identification
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Fruiting Body
Individual fruiting bodies are 0.39 to 1.2 inches (1 to 3 cm) across, but are typically fused into large patches (often over 50 cm long); gelatinous; lobed and brainlike; reddish-black to black; surface smooth or slightly rough.
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Spore Print
White.
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Habitat
It is saprobic, grows on recently fallen hardwood sticks and branches (especially oak), and is commonly found in North America during spring and fall, with occasional appearances during summer and winter. In Central Europe it is common in beech forestsю
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Microscopic Features
Spores 10-16 x 3-5 µ; sausage-shaped; smooth. Basidia longitudinally septate (cruciate), with sterigmata to 65 µ long. Clamp connections present.
Look-Alikes
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Has more button-shaped fruit bodies in clusters that quickly become deformed and coalesce, forming an effused, lobed mass that can be 3.9 inches (10 cm) or more across. The two species are indistinguishable microscopically, but DNA research indicates they are distinct.
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Has more erect fruit bodies without warts on the surface, lighter colors (ranging from yellowish brown to dark brown), and a small base.
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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.
History
There is some uncertainty about Witches' Butter classification. Some experts put it in the Tremellales order, while in the USA it's categorized under the Auriculariaceae family, while in Britain, it's under Exidiaceae. The French naturalist Jean Baptiste Francois (Pierre) Bulliard first described it in 1789 as Tremella glandulosa, but later the Swedish mycologist Elias Magnus Fries moved it to the Exidia genus. However, Fries used the name Exidia glandulosa for both Witches' Butter and another jelly fungus called Exidia plana. The two species were finally distinguished by Dutch mycologist Marinus Anton Donk.
The name Exidia means exuding or staining, which is fitting because this fungus looks like an exudation when it's wet and like a dark stain on wood when it's dry. The name glandulosa comes from the abundance of glands (papillae) on the surface of the fruitbodies of this fungus.
Synonyms and Varieties
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Tremella atra O.F. Müller (1782), Flora danica, 15, p. 5, tab. 884
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Tremella glandulosa Bulliard (1788), Herbier de la France, 9, tab. 420, fig. 1 (Basionyme) Sanctionnement : Fries (1822)
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Tremella glauca Persoon (1794), in Römer, Neues magazin für die botanik, 1, p. 111
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Peziza glandulosa (Bulliard) Schrader (1799), Journal für die botanik, 2(2), p. 59
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Tremella spiculosa Persoon (1800) [1799], Observationes mycologicae seu descriptiones tam novorum quam notabilium fungorum, 2, p. 99
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Tremella spiculosa var. ß glauca (Persoon) Persoon (1801), Synopsis methodica fungorum, p. 624
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Tremella arborea Smith (1812), English botany: or, coloured figures of British plants, Edn 2, tab. 2448
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Tremella flaccida Smith (1812), English botany: or, coloured figures of British plants, Edn 2, tab. 2452
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Gyraria spiculosa (Persoon) Gray (1821), A natural arrangement of British plants, 1, p. 594
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Auricularia glandulosa (Bulliard) Wahlenberg (1826), Flora suecica enumerans plantas sueciae indigenas, 1, p. 994
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Spicularia glandulosa (Bulliard) Chevallier (1826), Flore générale des environs de Paris, 1, p. 94
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Exidia spiculosa (Persoon) Sommerfeldt (1826), Supplementum florae lapponica, p. 307
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Exidia applanata Schweinitz (1832), Transactions of the American philosophical Society, series 2, 4(2), p. 185
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Exidia plicata Klotzsch (1839), in Dietrich, Flora reigni Borussici, Flora des Königreichs Preussen, 7, tab. 475
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Tremella cinerea Bonorden (1851), Handbuch der allgemeinen mykologie als anleitung zum studium derselben, p. 151
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Tremella nigra Bonorden (1851), Handbuch der allgemeinen mykologie als anleitung zum studium derselben, p. 151
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Tremella neglectaTulasne (1872), Annales des sciences naturelles, botanique, série 5, 15, p. 222
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Exidia glandulosa subsp.* plicata(Klotzsch) P. Karsten (1882), Bidrag till kännedom af Finlands natur och folk, 37, p. 198
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Exidia neglecta J. Schröter (1888) [1889], in Cohn, Kryptogamen-flora von Schlesien, 3(1), p. 393
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Tremella grilletii var. neglecta (Tulasne) Costantin & L.M. Dufour (1891), Nouvelle flore des champignons, Edn 1, p. 208
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Tremella faginea Britzelmayr (1895), Botanisches centralblatt, 62, p. 313, fig. 29
Photo sources:
Photo 1 - Author: Dan Molter (shroomydan) (CC BY-SA 3.0)
Photo 2 - Author: Nina Filippova (CC BY-SA 4.0)
Photo 3 - Author: Nova Patch (CC BY-SA 4.0)
Photo 4 - Author: aarongunnar (CC BY-SA 4.0)
Photo 5 - Author: Erik (Public Domain)