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Agaricus amicosus

[ Basidiomycetes > Agaricales > Agaricaceae > Agaricus . . . ]

Taxonomy in Transition: ...  > Agaricales > Lepiotoid Clade (J&V, 1998)

by Michael Kuo

Agaricus amicosus is a common fungal feature of Colorado's high-elevation conifers forests; it is particularly common under Engelmann Spruce and Subalpine Fir during the late summer monsoon season.

Physical features separating Agaricus amicosus from other Rocky Mountain Agaricus species include the light to medium brown fibers on the cap, the large size, and the red-staining flesh. Separation from similar species in other areas (including Agaricus fuscofibrillosus on the West Coast and Agaricus haemorrhoidarius in the east), in the event high elevation leaves you so light-headed that you forget you are in the mountains, can be accomplished through chemical and microscopic analysis (see below).


Ecology: Saprobic; growing scattered or gregariously in piled litter of Engelmann Spruce and Subalpine Fir; summer and fall; documented from southwestern to north-central Colorado and perhaps to be expected throughout the spruce-fir forests of the Rocky Mountains.

Cap: 7-18 cm; convex or blocky at first, becoming broadly convex; dry; whitish underneath brown, pressed-down fibers that remain tightly affixed or become aggregated into small scales; often bruising reddish.

Gills: Free from the stem; close; pink when young, often bruising reddish; later dark chocolate brown to blackish; covered when in the button stage with a whitish to brownish partial veil.

Stem: 4-12 cm long; up to 3 cm thick; more or less equal above a slightly to moderately swollen base; with a skirtlike, whitish to brownish ring; whitish; bruising reddish orange; fairly smooth; base sheathed in whitish to brownish veil material.

Flesh: White; changing to reddish or brownish red when sliced.

Odor and Taste: Odor not distinctive or sweet and fruity; taste similar.

Chemical Reactions: Cap surface sometimes (but not always) yellow with KOH.

Spore Print: Dark chocolate brown.

Microscopic Features: Spores: 5-8 x 4.5-6 µ; elliptical. Cheilocystidia up to 30 x 12 µ; clavate to cylindric.

REFERENCES: Kerrigan, 1989. (Kerrigan, 1989; Evenson, 1997.) Herb. Kuo 08100704.


Agaricus amicosus

Agaricus amicosus

Agaricus amicosus

Agaricus amicosus

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Kuo, M. (2007, October). Agaricus amicosus. Retrieved from the MushroomExpert.Com Web site: