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Leucoagaricus barssii

[ Basidiomycota > Agaricales > Agaricaceae > Leucoagaricus . . . ]

by Michael Kuo

Known primarily from North America's West Coast and Europe, Leucoagaricus barssii is a denizen of urban locations and back dunes, often growing alone in disturbed-soil locations. Like other lepiotoid mushrooms it features a white spore print and gills that are free from the stem. Species of Amanita also feature free gills and white spore prints, and can be difficult to separate—especially in the case of whitish-capped, rooting mushrooms like Leucoagaricus barsii, since several species of Amanita in the "Lepidella" subgenus are similar. However, there is no universal veil in Leucoagaricus barssii, so there are no veil remnants adhering to the edge of the cap or the base of the stem—and, under the microscope, the spores are dextrinoid (at least some of them), making Amanita an impossible identification choice.

The whitish, fibrillose cap that becomes fibrillose-scaly, the large ring on the stem, the absence of dramatic staining and bruising reactions, and microscopic features (see below) define Leucoagaricus barssii. On the West Coast of North America, Leucoagaricus barssii should be compared with Leucoagaricus leucothites (cap bald rather than fibrillose) and Agaricus californicus (spore print brown, young gills pink, cap not as fibrillose).

Lepiota barssii, Lepiota/Leucoagaricus pinguipes and Leucoagaricus macrorhizus are synonyms.

Thanks to Mila Visser 't Hooft for documenting, collecting, and preserving Leucoagaricus barssii for study; her collection is deposited in The Herbarium of Michael Kuo.


Note: A solitary, mature, and particularly fibrillose-scaly specimen is described.

Ecology: Saprobic, growing alone, scattered, or gregariously in landscaping areas, near waste places, on disturbed ground, and in woodchips–or in woods, or back dunes; summer and fall; originally described from Oregon; in North America found in California and the Pacific Northwest; also present in Europe and Australia. The illustrated and described collection is from California.

Cap: 13 cm across; broadly convex; dry; radially fibrillose to fibrillose-scaly; whitish overall, with a pale grayish brown center and hints of gray elsewhere; not bruising where handled.

Gills: Free from the stem; crowded; short-gills frequent; white; not staining.

Stem: 9 cm long; 2.5 cm thick at the midpoint; club shaped, with a tapered base that roots into the substrate; with a large, fibrillose, white ring; white, staining and bruising brownish; bald above the ring, and slightly fibrillose below; basal mycelium white.

Flesh: White; unchanging when sliced.

Odor and Taste: Not distinctive.

Spore Print: White.

Microscopic Features: Spores 6–9 x 4–5 µm; ellipsoid; smooth; hyaline in KOH; erratically dextrinoid. Basidia 22–25 x 5–6 µm; clavate; 4-sterigmate. Pleurocystidia not found. Cheilocystidia 30–50 x 6–16 µm; clavate, cylindric, or subutriform; smooth; thin-walled; hyaline in KOH. Pileipellis a cutis; elements 2.5–7.5 µm wide, smooth, hyaline in KOH; becoming gelatinized. Clamp connections not found.

REFERENCES: (S. M. Zeller, 1934) E. C. Vellinga, 2000. (Smith, Smith & Weber, 1979; Arora, 1986; Breitenbach & Kränzlin, 1995; Vellinga, 2001; Trudell & Ammirati, 2009; Vellinga, 2009; Buczacki et al., 2013; Desjardin, Wood & Stevens, 2015; Siegel & Schwarz, 2016; Lange, 2018; Kibby, 2020.) Herb. Kuo 09182004.

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


Leucoagaricus barssii

Leucoagaricus barssii

Leucoagaricus barssii

Leucoagaricus barssii

Leucoagaricus barssii

Leucoagaricus barssii

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Kuo, M. (2022, February). Leucoagaricus barssii. Retrieved from the MushroomExpert.Com Web site: