''Exidia nigricans'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

fungus A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Auriculariaceae The Auriculariaceae are a family (biology), family of fungi in the order (biology), order Auriculariales. Species within the family were formerly referred to the "heterobasidiomycetes" or "jelly fungi", since many have gelatinous basidiocarps (fr ...

. In the UK, it has the recommended English name of warlock's butter. It produces black, gelatinous

basidiocarps In fungi, a basidiocarp, basidiome, or basidioma () is the sporocarp of a basidiomycete, the multicellular structure on which the spore-producing hymenium is borne. Basidiocarps are characteristic of the hymenomycetes; rusts and smuts do no ...

(fruit bodies) and 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''.

Taxonomy

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 ''E. plana''. Changes in the starting point for fungal nomenclatureInternational code for botanical nomenclature http://ibot.sav.sk/icbn/main.htm delegitimized ''E. plana'', making ''E. nigricans'' the species' earliest name.Roberts, P. (2009). ''Exidia nigricans'': a new and legitimate name for ''Exidia plana''. ''Mycotaxon'' 109: 219–220. Molecular research has shown that ''E. nigricans'' has distinct

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

from ''E. glandulosa'', despite similarities, even on a microscopic level.Weiss, M & Oberwinkler, F. (2001). Phylogenetic relationships in ''Auriculariales'' and related groups – hypotheses derived from nuclear ribosomal DNA sequences. ''Mycological Research'' 105: 403–415.

Common name

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 ''E. glandulosa'' and the yellow ''

Tremella mesenterica ''Tremella mesenterica'' (common names include yellow brain, golden jelly fungus, yellow trembler, and witches' butter) is a common jelly fungus in the family Tremellaceae of the Agaricomycotina. The gelatinous, orange-yellow fruit body of th ...

''. It is said to be based on a folk belief that witches milk cows at night and scatter the butter they create in the process around.

Description

''Exidia nigricans'' forms dark sepia to blackish, rubbery-gelatinous fruit bodies that are button-shaped and across. The fruitbodies occur in clusters and quickly coalesce to form effused, irregular masses up to across. The upper,

spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...

-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 300px, Making a spore print of the mushroom ''Volvariella volvacea'' shown in composite: (photo lower half) mushroom cap laid on white and dark paper; (photo upper half) cap removed after 24 hours showing warm orange ("tussock") color spore print. ...

is white.Breitenbach, J. & Kranzlin, F. (1986). ''Fungi of Switzerland'' Vol. 2: 65 (as ''E. glandulosa'')

Microscopic characters

The microscopic characters are typical of the genus '' Exidia''. The

basidia A basidium (: basidia) is a microscopic spore-producing structure found on the hymenophore of reproductive bodies of basidiomycete fungi. The presence of basidia is one of the main characteristic features of the group. These bodies are also ...

are ellipsoid, septate, 15–25 × 8–13 μm. The spores are allantoid (sausage-shaped), 14–19 × 4.5–5.5 μm.

Similar species

''Exidia nigricans'' and ''E. glandulosa'' are frequently confused. The two are similar (even microscopically), but ''E. glandulosa'' produces discrete, top-shaped fruitbodies that rarely if ever coalesce. Fruitbodies of '' Phaeotremella foliacea'' and '' P. frondosa'' are typically a warmer, lighter brown, but can sometimes be dark sepia to black. The fruitbodies are gelatinous, but usually foliaceous (with flattish lobes or fronds) and never have warts or pegs on the surface. Non-gelatinous, black fruit bodies on wood occur in other genera, including '' Annulohypoxylon'', '' Biscogniauxia'', '' Camarops'', and '' Hypoxylon''.

Habitat and distribution

''Exidia nigricans'' is a wood-rotting species, typically found on dead attached branches of a wide range of broadleaf trees. It persists for some while on fallen branches and logs. The species typically fruits in autumn and winter. It is widely distributed in the Northern Hemisphere, including Europe and North America. In the latter, it can be found from November to March on the west coast, and around the year elsewhere.

References

{{Taxonbar, from=Q26203 Auriculariales Fungi of Europe Fungi of North America Fungi described in 1776 Fungus species