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Floccularia pitkinensis

[ Basidiomycota > Agaricales > Agaricaceae > Floccularia . . . ]

by Michael Kuo

Described in 1976 by Colorado mushroom expert Sam Mitchel and mycology icon Alexander Smith, Floccularia pitkinensis was originally collected in Aspen, which is in Pitkin County, Colorado. Like other species of Floccularia it features Tricholoma-like stature, attached gills, a white spore print, a sheathed stem, and amyloid spores. It can be distinguished from other Floccularia species on the basis of its cap, which is dingy brownish yellow and only a little scaly; Floccularia straminea is bright yellow and very scaly, while Floccularia albolanaripes can be similarly colored but usually somewhat brighter, especially when young—and the cap margin of Floccularia albolanaripes is usually yellow, even in maturity. Under the microscope, Floccularia pitkinensis has hyphae in the pileipellis that become a bit inflated, causing them to be constricted at the septa (see the illustration to the right), while the corresponding hyphae in Floccularia albolanaripes do not become inflated.

Armillaria pitkinensis is a previous name.


Ecology: Mycorrhizal with Engelmann spruce and subalpine fir; terrestrial, growing alone or scattered; late summer and fall; southern Rocky Mountains. The illustrated and described collection is from Colorado.

Cap: 2–4 cm; convex when young, becoming broadly convex; dry and shiny; innately appressed-fibrillose in sub-scaly, radial patterns; dull brownish golden; the margin adorned with white partial veil remnants.

Gills: Attached to the stem by a notch; close or nearly distant; short-gills frequent; white.

Stem: 2–3 cm long; about 1 cm thick; more or less equal; bald near the apex; sheathed below with shaggy, soft, white scales; with a bent-back, whitish ring; white.

Flesh: White; not changing on exposure.

Odor: Not distinctive.

Chemical Reactions: KOH on cap surface negative.

Spore Print: White.

Microscopic Features: Spores 6–8 x 3.5–5 µm; ellipsoid; smooth; weakly amyloid. Lamellar trama parallel. Basidia 30–35 x 6–7 µm; 4-sterigmate. Hymenial cystidia not found. Pileipellis a cutis; elements 5–10 µm wide, smooth, thin-walled, hyaline in KOH, often constricted at septa; terminal elements narrowing to a subacute apex; clamp connections present.

REFERENCES: (Mitchel & Smith, 1976) Bon, 1990. (Mitchel & Smith, 1976; Smith, Smith & Weber, 1979.) Herb. Kuo 08130804.

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Floccularia pitkinensis

Floccularia pitkinensis

Floccularia pitkinensis
Elements of the pileipellis

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Kuo, M. (2020, January). Floccularia pitkinensis. Retrieved from the MushroomExpert.Com Web site: