Hebeloma geminatum Beker, Vesterh. & U. Eberh.; Eberhardt, Beker & Vesterholt, Persoonia 35: 122, 2015.

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 geminatum Beker, Vesterh. & U. Eberh.; Eberhardt, Beker & Vesterholt, Persoonia 35: 122, 2015. Fig. 25

Macroscopic description.

Cap 2.0-12.0 cm in diameter, usually convex, sometimes broadly umbonate or applanate, margin usually smooth, occasionally involute, crenulate or upturned with age, tacky when moist, not hygrophanous usually uniformly colored, rarely bicolored, at center usually cream or whitish, sometimes a little yellowish, at margin paler, cream to whitish, without any traces of veil. Lamellae initially very pale brown, later clay-brown, adnate to emarginate, maximum depth 4-8 mm, number of lamellae {L} 62-100, with visible droplets and white fimbriate edge. Stem 1.5-11.0 × 0.7-1.5 {median} × 0.7-1.6 {base} cm, initially whitish, later pale brownish, initially pruinose, apex with watery droplets, cylindrical to clavate, stem Q (2.1-)2.5-9.2(-10.6), floccose. Context firm, stem interior stuffed, becoming hollow with age, flesh usually not discoloring from base. Smell raphanoid. Taste mild, raphanoid. Spore deposit brownish olive to grayish brown.

Microscopic description.

Spores amygdaloid, on ave. 10.0-11.0 × 5.5-6.5 µm, ave. Q = 1.7-1.9, grayish yellow to yellow-brown to brown, guttulate, weakly to distinctly ornamented (O2O3), perispore somewhat loosening ((P0) P1 (P2)), indextrinoid or indistinctly dextrinoid (D0D1). Basidia 25-35 × 7-9 µm, ave. Q = 3.3-4.3, mostly four-spored. Cheilocystidia clavate-stipitate or spathulate-stipitate and occasionally capitate-stipitate or clavate-lageniform, occasionally characteristically bifurcate, with a median wall thickening, septate or sinuate, on ave. 50-72 × 8-10.5 (apex) × 4-4.5 (middle) × 3.5-5 (base) µm, ratios A/M = 1.76-2.57, A/B = 1.68-2.85, B/M = 0.81-1.19. Epicutis an ixocutis, 110-200 µm thick (measured from exsiccata), maximum hyphae width 5-8 µm, variably encrusted, trama elements beneath subcutis cylindrical, ellipsoid, sausage-shaped up to 16 µm wide. Caulocystidia similar to cheilocystidia, up to 70 µm long and 12 µm wide.

Collections examined.

S-Greenland: Sermiliarsuk, Sioralik, Aasivii, 65.53°N, 48.33°W, 30 Aug 1997, T. Borgen (TB97.154a, C-F-103508), with Betula pubescens , 50 m. W-Greenland: Kangerlussuaq, c. 2 km W of the Airport, Mt. Hassel, 67.06°N, 50.68°W, 10 Aug 2000, A-M. Larsen, T. Borgen (TB00.065, C-F-103514), 50 m, with Salix glauca in copse. Kangerlussuaq, Hassells Fjeld, Kløftsøerne, 67.01°N, 50.71°W, 27 Aug 2018, H. Knudsen (HK18.379B, C-F-111117), 300 m, with Salix glauca , Betula nana in heathland.

Distribution.

Only known from two localities in southwestern Greenland. Generally distributed over much of Europe, but lacking in the Mediterranean region. Northernmost European localities are from Norway at just above 70°N. This species has already been recorded in North America (https://mycoportal.org/portal/collections/list.php, accessed 2 Dec 2020) but how common it is, is not yet known. Temperate and boreal, with a few records from the Low Arctic zone.

Habitat and ecology.

Only three collections with Salix glauca , Betula nana and B. pubescens , but when recorded on 27 Aug. 2018, on the south-exposed side of Mt. Hassell, it was numerous and, remarkably, the only agaric present. From Europe, there are a number of hosts recorded, including many deciduous and coniferous trees ( Beker et al. 2016).

Figures

Figure 25. Hebeloma geminatum A HK 18.379 B, photograph H. Knudsen B distribution of cited collections C spores x 1600 and D cheilocystidia x 1000 of HK 18.379 B in Melzer's reagent. Scale bars: 5 µm; microphotographs H. K. J. Beker.