What You Should Know
Collybia cirrhata is a species of fungus in the family Tricholomataceae of the order Agaricales (gilled mushrooms). It can be distinguished by its small, dingy white mycenoid fruitbodies that are usually found growing from the blackened remains of Russula or Lactarius species and the lack of a sclerotium at the base of the stipe. It is a saprobic species that grows in clusters on the decaying or blackened remains of other mushrooms.
The mushroom, although not poisonous, is considered inedible because of its insubstantial size.
Other names: Piggyback Shanklet.
Collybia cirrhata Mushroom Identification
Saprobic; growing gregariously on the blackened and sometimes nearly unrecognizable remains of mushrooms; found under hardwoods or conifers; summer and fall; widely distributed, at least in northern and montane North America.
3-11 mm; convex with an inrolled margin when young, becoming broadly convex to flat, with a central depression; dry or moist; bald; sometimes lined at the margin; whitish to faintly pinkish; fading.
Attached to the stem; close or almost distant; whitish.
1-2.5 cm long; 1 mm thick; more or less equal; dry; pliant; often minutely dusted; whitish; basal mycelium copious and white; with many small, white mycelial threads extending into the substrate.
Spores 5-6.5 x 2-3 µ; smooth; ellipsoid to sublacrymoid; inamyloid. Pleuro- and cheilocystidia absent. Pileipellis a cutis or ixocutis of cylindric elements 3-6.5 µ wide.
Collybia cirrhata is most likely to be confused with the remaining members of Collybia, which have a similar external appearance. C. tuberosa is distinguished by its dark reddish-brown sclerotia that resemble apple seeds, while C. cookei has wrinkled, often irregularly shaped sclerotia that are pale yellow to orange. Other similar mushrooms include Baeospora myosura and species of Strobilurus, but these species only grow on pine cones.
Collybia cirrhata Taxonomy and Etymology
The species first appeared in the scientific literature in 1786 as Agaricus amanitae by August Johann Georg Karl Batsch; Agaricus amanitae subsp. cirrhatus, proposed by Christian Hendrik Persoon in 1800, is considered synonymous. A later combination based on this name, Collybia amanitae, was published by Hanns Kreisel in 1987. However, Kreisel noted the combination to be "ined.", indicating that he did not believe the name to be validly published, according to article 34.1 of the rules for botanical nomenclature, which states: "A name is not validly published ... when it is not accepted by the author in the original publication."
The first correct name was published in 1803 by Heinrich Christian Friedrich Schumacher, who called the species Agaricus cirrhatus. French mycologist Lucien Quélet transferred it to Collybia in 1879, resulting in the binomial by which it is currently known. The species had also been transferred to Microcollybia by Georges Métrod in 1952 and again by Lennox in 1979 (because Métrod's transfer was considered a nomen nudum, and thus invalid according to nomenclatural rules); the genus Microcollybia has since been wrapped into Collybia.
Molecular phylogenetics have shown that C. cirrhata forms a monophyletic clade with the remaining two species of Collybia. Because C. cirrhata is the only one of the three Collybia species lacking sclerotia, it has been suggested that this character trait is an anapomorphy—that is, unique to a single, terminal species within a clade.
The specific epithet is derived from the Latin cirrata, meaning "curled". Charles Horton Peck called it the "fringed-rooted Collybia". In the United Kingdom, it is commonly known as the "piggyback shanklet".
Collybia cirrhata Synonyms
Agaricus amanitae Batsch (1786)
Agaricus amanitae subsp. cirrhata Pers. (1800)
Agaricus cirrhatus Schumach. (1803)
Sclerotium truncorum (Tode) Fr. (1822)
Microcollybia cirrhata (Schumach.) Georges Métrod (1952)
Microcollybia cirrhata (Schumach.) Lennox (1979)
Collybia amanitae (Batsch) Kreisel (1987)
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