Major Groups > Gilled Mushrooms > Dark-Spored > Agaricus > Agaricus chionodermus


Agaricus chionodermus

[ Basidiomycota > Agaricales > Agaricaceae > Agaricus . . . ]

by Michael Kuo

This is a whitish species from the western mountains, characterized by its large size, its habitat in spruce-fir or high-elevation pine forests, its gills, which remain pink for quite a while before turning brown, and microscopic features (see below). Agaricus chionodermus does not usually stain or bruise yellow on the cap or stem, like some similar species do, but the flesh in the base of the stem, when sliced, is often dull yellow. The odor is not distinctive.

Strictly speaking, Agaricus chionodermus is a European species, and it is unclear whether our North American version is the same, since "[c]larification of the relationship between our species and the European A. chionodermus must await sequencing of the latter species and clarification of its concept" (Kerrigan 2016).

Thanks to Laurence Boomer for collecting, documenting, and preserving some of the illustrated and described specimens; his collection is deposited in The Herbarium of Michael Kuo.


Ecology: Saprobic; growing gregariously under pines, spruces, or firs at high elevations; summer and fall; western mountains from New Mexico to Canada. The illustrated and described collections are from Colorado and Oregon.

Cap: 8–17 cm; convex or somewhat blocky at first, becoming broadly convex; dry; finely silky-fibrillose with whitish to brownish fibrils in places but usually smooth overall and not notably scaly; whitish; not bruising when rubbed.

Gills: Free from the stem; close or crowded; short-gills frequent; deep pink when young, becoming grayish pink, pinkish brown, and finally dark brown; when in the button stage covered with a whitish partial veil that may develop yellowish stains.

Stem: 7–15 cm long; 2–3 cm thick; more or less equal; finely silky or bald; with an ample, whitish, skirtlike ring that may develop yellowish stains; white, discoloring a little brownish; sometimes bruising yellow near the base; basal mycelium white.

Flesh: White overall, but usually dull yellow in the stem base; unchanging when sliced.

Odor and Taste: Odor faintly fragrant, or not distinctive; taste not distinctive.

Chemical Reactions: KOH negative on cap surface and stem surface, but yellow on flesh in stem base.

Spore Print: Dark brown.

Microscopic Features: Spores: 8–10 x 5–6.5 µm; ellipsoid; smooth; thick-walled; brown in KOH; brown in Melzer's. Basidia 4-sterigmate. Cheilocystidia sometimes not found; when present 25–40 x 7.5–10 µm; clavate to subclavate; smooth; thin-walled; hyaline in KOH. Pleurocystidia not found. Pileipellis a cutis; elements 2.5–10 µm wide, smooth, hyaline in KOH.

REFERENCES: A. Pilát, 1951. (Arora, 1986; Kerrigan, 2016.) Herb. Kuo 08160305, 08061003, 05281701.

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


Agaricus chionodermus

Agaricus chionodermus

Agaricus chionodermus

Agaricus chionodermus

Agaricus chionodermus

Agaricus chionodermus

Agaricus chionodermus

© MushroomExpert.Com

Cite this page as:

Kuo, M. (2018, April). Agaricus chionodermus. Retrieved from the MushroomExpert.Com Web site: