Hebeloma leucosarx P.D. Orton; Trans. Br. mycol. Soc. 43(2): 244, 1960.

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 leucosarx P.D. Orton; Trans. Br. mycol. Soc. 43(2): 244, 1960. Fig. 32

Macroscopic description.

Cap 1.8-9.0 cm in diameter, convex, later umbonate, sometimes turned upwards with age, margin often involute when young, later smooth or eroded or wavy, tacky when moist, rarely spotted, sometimes hygrophanous, usually bicolored, often with thin margin but may be unicolored when young, at center dark pinkish buff to ochraceous or dark olive buff or yellowish brown to clay buff or cinnamon to umber or brick, at margin cream to honey or pinkish buff to ochraceous or dark olive buff or clay-pink, without any remains of veil. Lamellae light gray brown to vinaceous buff, adnate to emarginate, maximum depth 2.5-9 mm, number of lamellae {L} 50-70, droplets usually visible but sometimes absent, white fimbriate edge present. Stem (3.0-)3.7-11.0 × 0.3-1.4 {median} × 0.8-2.0 {base} cm, stem Q (6-)6.8-14(-17.5), whitish, often clavate to bulbous, sometimes cylindrical, pruinose to floccose, particularly at apex, sometimes more velutinate, sometimes with mycelial chords. Context firm, stem interior hollow, sometimes with superior wick, flesh discoloring from base. Smell raphanoid, sometimes with hint of cacao. Taste raphanoid, sometimes weakly bitter. Spore deposit brownish olive to umber.

Microscopic description.

Spores amygdaloid, occasionally limoniform, not or weakly papillate, on ave. 9.5-12.0 × 5.5-7.0 µm, ave. Q = 1.6-2.0 yellow brown to brown, guttulate, almost smooth to weakly ornamented but occasionally distinctly ornamented (O1O2O3), perispore not or somewhat loosening (P0P1), weakly to strongly dextrinoid, reaction often very slow (D2D3 (D4)). Basidia 24-33(-35) × 7-8(-10) µm, ave. Q = 3-4.1, mostly four-spored. Cheilocystidia slenderly clavate, occasionally clavate-stipitate or ventricose, occasionally with characteristic apical wall thickening, occasionally bifurcate, geniculate or septate, on ave. 41-67 × 6.5-8.5 (apex) × 4-5.5 (middle) × 4.5-6.5 (base) µm, ratios A/M = 1.42-1.72, A/B = 1.15-1.68, B/M = 0.94-1.33. Epicutis an ixocutis, 80-200 thick (measured from exsiccata), maximum hyphae width 5 µm, sometimes encrusted, trama elements beneath subcutis ellipsoid to sausage-shaped, occasionally polygonal up to 20 µm wide. Caulocystidia similar to cheilocystidia, up to 200 µm long, often septate and markedly lageniform.

Collections examined.

S-Greenland: Paamiut, head of Eqaluit, median part, 62.03°N, 49.25°W, 15 Aug 1998, T. Borgen (TB98.119, C-F-103513), 300 m, with Betula glandulosa and Salix glauca in heathland. Paamiut, Taartoq/ Mørke Fiord, 62.01°N, 49.26°W, 29 Aug 1981, T. Borgen (TB81.211, C-F-103551), ca. 100 m, with Betula glandulosa in heathland.

Distribution.

Only two records, both from the same area. The general distribution of the species is temperate, to the middle boreal zone. The Greenland records are both from low arctic areas. Hebeloma leucosarx is missing from lowland regions of southern Europe ( Beker et al. 2016; Grilli et al. 2020).

Habitat and ecology.

Among the 28 species of Hebeloma found in Greenland, H. leucosarx is the only species that may primarily be associating with Betula rather than Salix , based on the observations of Beker et al. (2016) from Europe. According to their monograph, in Europe, the main hosts are conifers and Betula ( Beker et al. 2016); for the above records, the host is most likely B. glandulosa , although in one record S. glauca is mentioned as present.

Figures

Figure 32. Hebeloma leucosarx A JV 06 - 757 (from Denmark), photo J. Vesterholt, reproduced by kind permission from Beker et al. (2016) B distribution of cited collections C spores x 1600 and D cheilocystidia x 1000 of TB 81.211 in Melzer's reagent. Scale bars: 5 µm; microphotographs H. K. J. Beker.