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Calocybe fallax

[ Basidiomycetes > Agaricales > Lyophyllaceae > Calocybe . . . ]

by Michael Kuo

Here is a brightly colored collybioid mushroom from northern and montane North America, usually found under conifers but occasionally found under oaks, alders, and other hardwoods. Distinguishing features include the yellow cap, gills, and stem; the small size (caps are under 3 cm across at maturity); the white spore print; and microscopic features (see below).

The European species Calocybe chrysenteron is nearly identical to the naked eye; however, under the microscope it features a pileipellis disposed as a cutis (as opposed to the hymeniform pileipellis of Calocybe fallax). It does not appear to occur in North America, despite a few herbarium records that probably represent misidentifications.

There is a bona fide nomenclatural nightmare surrounding the mushroom described here; competing names for the same mushroom include Calocybe naucoria and Rugosomyces fallax. The nightmare extends all the way back to C. H. Peck (1873), who named the species Agaricus fallax when there was already another mushroom bearing the name Agaricus fallax (it's now called Russula fragilis, in case that matters to you), and to Singer (1943, 1962) and, more recently, to an attempt to straighten out the mess by Redhead and Singer (1978) that apparently made things worse (according to the Index Fungorum) by neglecting to recognize that naucoria should be the species epithet. Oh, and the Europeans constantly argue over whether we should really use the genus name Rugosomyces instead of Calocybe. Can you tell that I don't care very much about this? If you do care, therefore, I hope you will consult a more reliable nomenclatural mess-sorter-outer than this webpage.


Ecology: Probably saprobic; growing alone, scattered, or gregariously in needle duff under conifers (including grand fir, subalpine fir, balsam fir, Engelmann spruce, and lodgepole pine) or in leaf litter under hardwoods (including oaks and alders); summer and fall; northern and montane North America.

Cap: 5-30 mm; broadly convex becoming broadly bell-shaped, flat, or shallowly depressed; soft; dry; bald; yellow to orangish yellow or brownish yellow; often fading markedly as it dries out; margin at first somewhat inrolled.

Gills: Attached to the stem, sometimes by means of a notch; crowded; pale yellow.

Stem: 2-4 cm long; 1-5 mm wide; more or less equal; dry; finely silky, or nearly bald; colored like the cap; basal mycelium whitish.

Flesh: Pale yellow.

Odor & Taste: Not distinctive.

Spore Print: White.

Microscopic Features: Spores 3-4 x 2-2.5 µ; elliptical; smooth; inamyloid. Cystidia absent. Basidia with siderophilous granules. Pileipellis hymeniform; elements hyaline to yellowish in KOH; terminal cells clavate to pyriform, 18-25 x 8-10 µ. Clamp connections present.

REFERENCES: Redhead & Singer, 1978. (Peck, 1873 [Agaricus fallax]; Saccardo, 1887; Smith, 1942 [Tricholoma fallax]; Singer, 1943 [Calocybe naucoria]; Singer, 1978 [Calocybe naucoria]; Brunner & Miller, 1988; McNeil, 2006; Kalamees in Knudsen & Vesterholt, 2008 [Rugosomyces fallax].) Herb. Kuo 08281104.

This site contains no information about the edibility or toxicity of mushrooms.


Calocybe fallax

Calocybe fallax

Calocybe fallax

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Kuo, M. (2013, February). Calocybe fallax. Retrieved from the MushroomExpert.Com Web site: