Hebeloma vaccinum Romagn., Bull. Trimest. Soc. Mycol. Fr. 81: 333 (1965)

Cripps, Cathy L., Eberhardt, Ursula, Schuetz, Nicole, Beker, Henry J., Vera S. Evenson, & Horak, Egon, 2019, The genus Hebeloma in the Rocky Mountain Alpine Zone, MycoKeys 46, pp. 1-54 : 14

1. Hebeloma vaccinum Romagn., Bull. Trimest. Soc. Mycol. Fr. 81: 333 (1965) Figures 4D, 7, 23 (1)

Etymology.

From vaccinus, meaning dun color (i.e. dull grayish brown).

Description.

Cortina not observed. Pileus 10-11 mm in diameter, convex, buff to brownish with a hoary coating, rather unicolor, smooth, shiny, tacky; margin turned down, a bit crenulate, faintly striate; edges white. Lamellae adnexed, L = 38 plus lamellulae, buff to milk coffee. Stipe 10 × 3 mm, equal, cream, finely floccose at apex and fibrillose for length, delicate. Context cream. Odor not apparent, but previously noted as raphanoid. Exsiccate: very tiny, brown, not shiny, lamellae not blackening.

Basidiospores yellowish brown, amygdaliform, limoniform, with a snout and small apiculus, distinctly verrucose (O3), with loosening perispore observed in a few spores (P1, P2), dextrinoid (D3), 10-14 × 6-8 µm, on average 12.2 × 7.1 µm, Q = 1.71; some larger spores present -18 × -9 µm. Basidia 27-35 × 7-9 µm, four-spored, possibly a few two-spored because of larger spores present. Cheilocystidia clavate-lageniform, some slightly more swollen at apex, 35-70 × 6-8 µm at apex, 3-5 µm in middle, and 6-10 µm at base, occasionally septate, no thickening observed. Pleurocystidia absent. Epicutis thickness 40-125 µm, with some encrusted hyphae.

Rocky Mountain Ecology

results are based on a single collection of two small basidiomes found in the Colorado alpine with Salix arctica .

Rocky Mountain specimen examined.

U.S.A. COLORADO: San Juan County, San Juan Mountains, Mineral Basin, with Salix arctica , 3320 m, 31 July 2002, CLC1881 (MONT), C. Cripps.

Discussion.

Beker and co-workers ( Beker et al. 2016; Eberhardt et al. 2016; including ML ITS analyses) showed that H. vaccinum can be recognized by its ITS region from all species apart from H. cavipes Huijsman, which differs in morphology and ecology. The RM H. vaccinum collection fits in with the diversity found within the species (Fig. 4D) it differs in 0-5 [0] bp from other included members of the species. The intraspecific variation of the included FE members of H. vaccinum is 0-8 [0] bp.

This species is usually described as larger (13-40 mm) than the Rocky Mountain specimens described here. Microscopically, the species has spores that are strongly dextrinoid (D3) with a frequently loosening perispore. The spores and cheilocystidia characteristics (swollen at the apex and at the base but constricted in the middle part) put it in H. sect. Denudata , subsect. Clepsydroida . Hebeloma vaccinum is known to occur in low elevation dunes and woodlands with Salix ; it is widespread in Northern Europe. Other arctic-alpine collections are from the European Alps, the Carpathians in Slovakia, and Greenland, always with Salix species ( Beker et al. 2016; Eberhardt et al. 2015b). It could be recognized in the Rocky Mountains by its association with dwarf Salix , small size, lack of a veil, and distinct spores and cystidia; compare with H. aurantioumbrinum .