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Rhodocollybia butyracea

[ Basidiomycetes > Agaricales > Marasmiaceae > Rhodocollybia . . . ]

by Michael Kuo

Rhodocollybia butyracea is a widespread decomposer of conifer debris, usually found under pines (species of Pinus, with bundled needles). It is very similar to Gymnopus dryophilus, but it tends to have a reddish brown, rather than yellow-brown, cap. Additionally, its stem is frequently somewhat club-shaped and its gills are often finely jagged--features not usually found in the straight-stemmed, even-gilled Gymnopus dryophilus. Several field guides emphasize a difference in spore print color (yellowish for Rhodocollybia butyracea; white for Gymnopus dryophilus), but the difference, which is minimal at best, requires a very thick spore print, natural lighting, and good eyes. The best means of separating the two species is microscopic; Rhodocollybia butyracea features dextrinoid, rather than inamyloid, spores.

DNA analysis by Mata and collaborators (2004) revealed at least two genetically distinct populations within "Rhodocollybia butyracea"; further research may determine that there is more than one species involved.


Ecology: Saprobic; decomposing the litter of conifers--especially pines; late summer and fall (also winter and spring in warmer climates); fairly widely distributed in North America.

Cap: 2-10 cm across; convex, becoming broadly convex or nearly flat; moist when fresh; bald; reddish brown, fading to cinnamon.

Gills: Narrowly attached to the stem or nearly free from it; close or crowded; whitish, sometimes developing pinkish tones with age; often developing finely jagged edges.

Stem: Up to 10 cm long and 1 cm thick; usually slightly to moderately club-shaped; moist or dry; bald; whitish to buff above; colored like the cap below; becoming hollow.

Flesh: Whitish.

Odor and Taste: Not distinctive.

Spore Print: Pale yellowish, pale pinkish, or merely white.

Microscopic Features: Spores smooth; 6-10.5 x 3.5-5 µ; elliptical; at least a few (often many) dextrinoid. Pleurocystidia absent. Cheilocystidia inconspicuous; subclavate to subcylindric; often lobed or with projections; up to 35 µ long. Pileipellis at maturity a densely interwoven cutis of cylindric elements 3-6 µ wide.

Collybia butyracea is a synonym.

REFERENCES: (Bulliard, 1792) Lennox, 1979. (Fries, 1821; Saccardo, 1887; Kauffman, 1918; Coker & Beardslee, 1921; Smith, Smith & Weber, 1979; Halling, 1983; Arora, 1986; Phillips, 1991/2005; Evenson, 1997; Barron, 1999; Halling, 2004; McNeil, 2006; Miller & Miller, 2006; Trudell & Ammirati, 2009.) Herb. Kuo 08120701, 10280705.

Further Online Information:

Rhodocollybia butyracea at Roy Halling's Collybia site
Rhodocollybia butyracea at MykoWeb
Collybia butyracea at Roger's Mushrooms


Rhodocollybia butyracea

Rhodocollybia butyracea

Rhodocollybia butyracea

Rhodocollybia butyracea

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Kuo, M. (2008, May). Rhodocollybia butyracea. Retrieved from the MushroomExpert.Com Web site: