Hebeloma subconcolor Bruchet; Bull. mens. Soc. linn. Lyon 39 (6 (Suppl.)): 127, 1970.

Eberhardt, Ursula, Beker, Henry J., Borgen, Torbjorn, Knudsen, Henning, Schuetz, Nicole & Elborne, Steen A., 2021, A survey of Hebeloma (Hymenogastraceae) in Greenland, MycoKeys 79, pp. 17-118 : 17

Hebeloma subconcolor Bruchet; Bull. mens. Soc. linn. Lyon 39 (6 (Suppl.)): 127, 1970. Fig. 33

Macroscopic description.

Cap 0.8-2.1 cm, convex to umbonate, sometimes broadly, margin smooth, sometimes involute, tacky when moist, usually almost unicolored, at center clay buff to gray brown to dark olive buff to sepia, sometimes pruinose particularly when young, margin sometimes paler, even cream, veil absent. Lamellae when young whitish, later distinctly gray, adnate to emarginate, 3-4 mm broad, number of lamellae {L} 20-32, droplets usually visible with naked eye, but occasionally only with × 10 lens or absent, edge white fimbriate. Stem 1.5-4.5 × 0.3-0.6 cm, {median} × 0.35-0.75 {base} mm, velute, usually pruinose at apex, cylindrical, base clavate or sometimes bulbous. Context firm, in stem stuffed, later hollow, discoloring brownish from base. Smell raphanoid, sometimes strongly. Taste bitter, raphanoid. Spore deposit clay buff.

Microscopic description.

Spores amygdaloid, limoniform, sometimes weakly papillate, on ave. 10.5-12.5 × 6.5-7.0 µm, ave. Q 1.6-1.85, usually guttulate, pale, yellow brown to brown, almost smooth to very weakly ornamented (O1O2), perispore not or somewhat loosening (P0P1), weakly to rather strongly dextrinoid (D2D3). Basidia 26-33(-36) × 8-9 µm, Q = 3.4-3.9, mostly four-spored. Cheilocystidia slenderly clavate, sometimes cylindrical, clavate-lageniform or ventricose, occasionally with a characteristic apical wall thickening, occasionally bifurcate, geniculate or septate, on ave. 47-69 × 6.5-9 (apex) × 5-6.5 (middle) × 5-7.5 (base) µm, ratios A/M = 1.36-1.71, A/B = 1.22-1.86, B/M = 0.92-1.26. Epicutis an ixocutis, 60-75 µm (measured from dried specimens), maximum hyphae width 5.5-6 µm, sometimes encrusted, shape of trama elements beneath subcutis ellipsoid, isodiametric, sausage-shaped up to 20 µm wide. Caulocystidia similar to cheilocystidia, up to 120 µm long and 11 µm wide, multi-septate.

Collections examined.

S-Greenland: Kangilinnguit-Ivittuut, 61.21°N, 48.12°W, 18 Aug 2018, H. Knudsen (HK18.232, C-F-111111), 125 m, in tundra. Narsarsuaq, 61.17°N, 45.40°W, 17 Aug 2015, H. Knudsen (HK15.089, C-F-8242), 60 m, with Salix glauca . Nuuk, Qooqqut, 64.26°N, 50.92°W, 15 Aug 1987, T. Borgen (TB87.117, C-F-4002), ca. 30 m, with Salix glauca in ditch. Paamiut, 61.99°N, 49.66°W, 4 Aug 1993, E. Rald (ER 93.168, C-F-104313), 25 m. Paamiut, 62.01°N, 49.4°W, 14 Aug 1990, T. Borgen (TB90.033, C-F-104299), 25 m. Paamiut, N of the Navigation School area, 62.02°N, 49°W, 3 Aug 1990, T. Borgen (TB90.018, C-F-119761), ca. 40 m, with Bistorta vivipara and Salix herbacea . W-Greenland: Disko, Fortune Bay, 69.31°N, 53.88°W, 3 Aug 1986, T. Borgen (TB86.122, C-F-103587), 20 m. Sisimiut, south of town, 66.95°N, 53.66°W, 18 Aug 2016, S.A. Elborne (SAE-2016.090-GR, C-F-106739), 20 m, with Salix glauca in copse. E-Greenland: Jameson Land, Constable Pynt, Ugleelv, 70.88°N, 22.85°W, 24 Jul 1989, H. Knudsen (HK89.302, C-F-2195), 100 m.

Distribution.

Hebeloma subconcolor is a truly arctic-alpine species with nine records from low and high arctic areas in Greenland. It was recently reported from two collections from alpine North America (Colorado, Cripps et al. 2019), but the records here are the first from arctic North America. Described from the European Alps by Bruchet 50 years ago, it is still only known from few other locations and it must be considered a rather rare species.

Habitat and ecology.

Nine collections of H. subconcolor are verified, but only sparse info is given on hosts and ecology. Salix glauca , S. herbacea and Bistorta vivipara are mentioned as possible hosts. Most localities are on acid soil in agreement with the conclusion of Beker et al. (2016), who, in Europe, had S. herbacea listed as possible host for each cited collection of the species.

Figures

Figure 33. Hebeloma subconcolor A SAE- 2016.090, photograph S. A. Elborne B distribution of cited collections C spores x 1600 and D cheilocystidia x 1000 of SAE- 2016.090 in Melzer's reagent. Scale bars: 5 µm; microphotographs H. K. J. Beker.