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Tricholoma arvernense

[ Basidiomycota > Agaricales > Tricholomataceae > Tricholoma . . . ]

by Michael Kuo

Tricholoma arvernense is a European species in the Tricholoma sejunctum species group, characterized by its yellow to orangish cap color, small spores, abundant clamp connections, and association with pines or, rarely, fir. In North America, the name is currently being applied to an Oregon and northern California Tricholoma that matches some of these features (the cap color and the small spores) and, apparently, in "DNA sequencing," according to unpublished results mentioned in Bessette and collaborators (2013).

There are differences, however: the Oregon species has "rare to occasional" clamp connections (Bessette et al. 2013)—or, in the collection I have studied, none (at least, in the amount of time I'm willing to devote to isolating and examining hyphal septa on a Thursday morning in late September); additionally the Oregon species is not a pine associate, but appears with other conifers (spruce, fir, hemlock)—although Siegel and Schwarz (2016) apply the name to a coastal California species associated with pines.

The description of Tricholoma tumidum in Shanks (1994) appears to represent what is now being called Tricholoma arvernense.

Thanks to Wendell Wood for collecting, documenting, and preserving Tricholoma arvernense for study; his collection is deposited in The Herbarium of Michael Kuo.


Ecology: Mycorrhizal with conifers—in Europe, primarily with pines, but in North America apparently with other conifers (possibly spruce, fir, and/or hemlock); growing alone, scattered, or gregariously; late summer and fall; Pacific Northwest. The illustrated and described collection is from Oregon.

Cap: 5–8 cm across; at first convex with a central bump, becoming broadly convex to broadly bell-shaped; dry; finely, radially appressed-fibrillose with brownish yellow fibrils on a yellowish ground or, near the margin, a whitish ground; the center usually darker and more brown.

Gills: Attached to the stem by a notch; close; short-gills frequent; whitish, sometimes staining or discoloring yellow, especially toward the cap margin.

Stem: 4–8 cm long; 1–2 cm thick; equal, or slightly swollen in the middle; bald; dry; whitish, developing brownish stains in places; basal mycelium white.

Flesh: White; unchanging when sliced.

Odor and Taste: Mealy.

Spore Print: White.

Microscopic Features: Spores 4–6 x 3.5–4.5 µm; ellipsoid, with a small apiculus; smooth; hyaline in KOH; inamyloid. Lamellar trama parallel. Basidia 4-sterigmate; 25–38 x 5–7 µm; clavate. Cheilocystidia 20–50 x 10–20 µm; clavate to sphaeropedunculate or irregular; smooth; hyaline in KOH. Pileipellis a cutis; elements 5–7.5 µm wide, smooth, hyaline in KOH. Clamp connections not found.

REFERENCES: Bon, 1976. (Shanks, 1994; Bessette et al., 2013; Christensen & Heilmann-Clausen, 2013; Siegel & Schwarz, 2016; Heilmann-Clausen et al., 2017.) Herb. Kuo 09261204.

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Tricholoma arvernense

Tricholoma arvernense

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Kuo, M. (2019, September). Tricholoma arvernense. Retrieved from the MushroomExpert.Com Web site: