What You Should Know
Collybia tuberosa is an inedible species of fungus in the family Tricholomataceae, and the type species of the genus Collybia. Like the two other members of its genus, it lives on the decomposing remains of other fleshy mushrooms. The fungus produces small whitish fruit bodies with caps up to 1 cm (0.4 in) wide held by thin stems up to 5 cm (2.0 in) long.
On the underside of the cap are closely spaced white gills that are broadly attached to the stem. At the base of the stem, embedded in the substrate is a small reddish-brown sclerotium that somewhat resembles an apple seed.
The appearance of the sclerotium distinguishes it from the other two species of Collybia, which are otherwise very similar in overall appearance. C. tuberosa is found in Europe, North America, and Japan, growing in dense clusters on species of Lactarius and Russula, boletes, hydnums, and polypores.
Other names: Lentil Shanklet, The Appleseed Coincap.
Collybia tuberosa Mushroom Identification
Saprobic; growing gregariously on the remains of decayed mushrooms (especially Lactarius and Russula species), or occasionally on humus; found under hardwoods or conifers; summer and fall (or in winter in warm climates); widely distributed in North America.
2-10 mm, convex with a somewhat inrolled margin when young, becoming broadly convex to flat, with a central depression; dry or moist; more or less bald; sometimes lined on the margin; whitish.
Attached to the stem; close or almost distant; whitish or pale pinkish.
1-5 cm long; about 1 mm thick; more or less equal; dry; often minutely dusted at the apex and/or base; whitish to pinkish; becoming hollow; attached to sclerotia which are tear-shaped or elliptical, reddish-brown, and measure 3-12 x 2-5 mm.
Spores 4-6 x 3-3.5 µ; smooth; ellipsoid to sublacrymoid; inamyloid. Pleurocystidia absent. Cheilocystidia present but scattered, rare, and inconspicuous; 18-32 µ long; cylindric, with occasional lobes or projections. Pileipellis a cutis or ixocutis of hyphae 2-5 µ wide; pileocystidia absent.
Collybia tuberosa Look-Alikes
Looks similar when seen from above, but as well as growing on wood it differs in producing brown spores.
Is similar in size and appearance to C. tuberosa, but grows on spruce and Douglas-fir cones.
Is smaller and grows on the cones of Magnolias.
Has roughly spherical, light brown to yellowish sclerotia.
Does not produce sclerotia. In the field, C. tuberosa may be distinguished from C. cookei by its dark reddish-brown sclerotia that somewhat resembles an appleseed. A microscope provides a more definitive way of distinguishing the two: the hyphae in the sclerotia of C. cookei are rounded, while those of C. tuberosa are elongated; this diagnostic character is apparent with both fresh and dried material of the two species.
Collybia tuberosa Taxonomy and Etymology
This mushroom was first described scientifically in 1792 by pioneering French mycologist Jean Baptiste Francois (Pierre) Bulliard, who named it Agaricus tuberosus.
German mycologist Paul Kummer transferred this species to the genus Collybia in 1871, establishing its currently-accepted scientific name Collybia tuberosa.
Synonyms of Collybia tuberosa include Agaricus tuberosus Bull., Sclerotium cornutum Fr., Gymnopus tuberosus (Bull.) Gray, and Marasmius sclerotipes Bres.
The generic name Collybia means 'small coin', which is a reference to the round flattish caps typical of many collybioid mushrooms. The specific epithet tuberosa comes from Latin and simply means tuberous and refers to the tuberous base of the stem of this mushroom.
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