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Agaricus subperonatus

by Michael Kuo, 10 September 2024

Agaricus subperonatus is a brown-capped European and North American species found growing near conifers—usually pines—in urban settings like parks, yards, and gardens. Like other species of Agaricus it features gills that are free from the stem, and a dark brown spore print. Although some of its features are variable, it can be tentatively recognized by the brown cap and habitat, together with the fact that its stem usually roots deeply into the substrate and features a ring. Distinctive microscopic features include the medium-sized spores (on the Agaricus scale) and plentiful clavate cheilocystidia.

And now the variability. The sliced flesh sometimes stains pinkish to reddish (but never yellow)—and sometimes it doesn't. The cap ranges from fibrillose to sub-scaly to decidedly scaly with contrasting brown scales. The lower stem often, but not always, features evidence of a universal veil, in the form of ephemeral to prominent whitish to brown bands or vague zones.

Because of the variability in features, this mushroom has been described several times. Synonyms include Agaricus vaporarius and Agaricus cappellianus.

Description:

Note: A single collection is described here; be sure to read the discussion of morphological variability for this species, above.

Ecology: Saprobic; growing gregariously in urban areas in association with conifers (usually pines), often but not always in grass; summer and fall; originally described from temperate Europe (Persoon 1801); widespread in Europe; in North America documented in the Midwest and in the Denver area. The illustrated and described collection is from Missouri.

Cap: 6–9 cm; convex, becoming broadly convex; dry; innately fibrillose or scaly; overall brownish to medium brown; the young margin often adorned with remnants of the partial veil.

Gills: Free from the stem; crowded; short-gills frequent; at maturity dark brown.

Stem: 5–7 cm long; 1–1.5 cm thick; tapered to the base; with a white ring and, below it, scattered and vague zones of universal veil; whitish; bald; basal mycelium white.

Flesh: Whitish; not changing when sliced.

Odor and Taste: Not distinctive.

Chemical Reactions: KOH negative on cap surface.

Spore Print: Dark brown.

Microscopic Features: Spores 6–8 x 4–5.5 µm; ellipsoid, with a prominent apiculus; smooth; thick-walled; brown in KOH. Basidia 4-sterigmate. Pleurocystidia not found. Cheilocystidia 20–30 x 6–8 µm; clavate or subclavate; smooth; thin-walled; septate; hyaline in KOH. Pileipellis a cutis; elements 5–10 µm wide, smooth, hyaline to brown in KOH.

REFERENCES: (J. E. Lange, 1926) R. Singer, 1951. (Persoon, 1801; Phillips, 1981; Cappelli, 1984; Breitenbach & Kränzlin, 1995; Nauta, 2001; Boccardo et al., 2008; Kerrigan, 2016; Læssøe & Petersen, 2019; Kibby, 2021.) Herb. Kuo 11051701.

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Spores

Cheilocystidia

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Kuo, M. (2024, September). Agaricus subperonatus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/agaricus_subperonatus.html