Hebeloma mesophaeum (Pers.) Quel .; Mem . Soc. Emul . Montbeliard , Ser . 2, 5: 128, 1872.

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 mesophaeum (Pers.) Quel.; Mem. Soc. Emul. Montbeliard, Ser. 2, 5: 128, 1872. Fig. 16

Macroscopic description.

Cap 0.7-6.5 cm in diameter, convex when young, usually becoming umbonate, sometimes papillate, margin sometimes involute when young, occasionally crenulate, often eroded, upturned or radially split when older, tacky when moist, not hygrophanous, usually bicolored, rarely unicolored, at center dark pinkish buff to dark olive buff to grayish brown to umber or brownish olive to sepia to clay-buff or cinnamon or yellowish brown to orange brown or dark brick, at margin cream to pinkish buff to grayish buff or clay-buff to dark olive buff to grayish brown or brownish olive to grayish pink, with remains of universal veil, partial veil present. Lamellae when young pale brown, when older ochre brown to fairly dark brown, adnate to emarginate, sometimes with decurrent tooth, rarely decurrent, maximum depth up to 6.5 mm, number of lamellae {L} 30-48, droplets absent, but occasionally visible with × 10 lens or rarely visible with naked eye, white fimbriate edge usually present, sometimes weak. Stem 1.4-8.0(-9.0) × (0.2-)0.3-0.6(-0.8) cm, whitish then pale sordid gray brown, already when young dark sordid brown at base, when young with brownish tomentose velar remnants downwards, cylindrical, rarely tapering or clavate, stem Q (4.3-)4.8-16.3(-18.8), fibrillose, usually pruinose to floccose at apex. Context firm, stem interior stuffed, later hollow, occasionally with superior wick, stem flesh discoloring from base, sometimes very strongly, rarely absent. Smell usually raphanoid, rarely absent. Taste mild to bitter, sometimes raphanoid. Spore deposit dark olive buff to brownish olive to umber.

Microscopic description.

Spores ellipsoid, occasionally ovoid, on ave. 8.0-10.5 × 4.5-6.0 µm, Q = 1.3-1.9, (but see the notes below) yellow through yellow brown to brown, guttulation variable, almost smooth to weakly ornamented (O1O2), perispore not or somewhat loosening (P0P1), indistinctly dextrinoid (D0D1). Basidia 24-31(-32) × 7-9 µm; ave. Q = 3.2-4, mostly four-spored. Cheilocystidia lageniform, ventricose, occasionally cylindrical or rarely clavate, occasionally with characteristic apical or basal wall thickening, sometimes bifurcate, geniculate or septate (sometimes clamped), on ave. 26-62 × 4-6 (apex) × 3.5-6 (middle) × 6-11 (base) µm, ratios A/M = 0.94-1.25, A/B = 0.45-0.98, B/M = 1.36-2.19. Epicutis an ixocutis, 60-350 µm thick (measured from exsiccata), maximum hyphae width 3-10 µm, encrustation variable, trama elements beneath subcutis angular or isodiametric to ellipsoid or cylindrical to sausage-shaped up to 22 µm wide. Caulocystidia similar to cheilocystidia, but less ventricose, up to 130 µm long.

Collections examined.

S-Greenland: Paamiut, 62°N, 49.67°W, 6 Sep 1990, T. Borgen (TB90.086, C-F-76757), 20 m, with Salix glauca . Paamiut, 62.01°N, 49.67°W, 17 Aug 1990, T. Borgen (TB90.040, C-F-119759), 30 m, with Bistorta vivipara . W-Greenland: Kangerlussuaq, 67.01°N, 50.72°W, 2 Aug 2016, T. Borgen (TB16.038, C-F-104301), 50 m, with Salix glauca in tundra. Kangerlussuaq NE, near a glacier, 67.02°N, 50.66°W, 12 Aug 2000, E. Ohenoja (EO12.8.00.1, OULU F050224), 40 m, in heathland. Kangerlussuaq, Sandflugtsdalen, near the ice cap, 67.0578°N, 50.4571°W, 12 Aug 2000, T. Borgen (TB00.088, C-F-137116), 50 m. Kangerlussuaq, Sandflugtsdalen, 67.06°N, 50.46°W, 12 Aug 2000, T. Borgen (TB00.093, C-F-103521), 50 m, with Salix glauca in dunes. Kangerlussuaq, Sandflugtsdalen, 67.06°N, 50.46°W, 12 Aug 2000, T. Borgen (TB00.094, C-F-103522), 200 m, with Salix glauca in dunes. Kangerlussuaq, Sandflugtsdalen, 67.06°N, 50.46°W, 12 Aug 2000, A-M. Larsen, T. Borgen (TB00.091, C-F-103520), 50 m, with Salix glauca in dunes. Kangerlussuaq, Sandflugtsdalen, c. 15 km E of airport, 67.06°N, 50.46°W, 2 Aug 2016, T. Borgen (TB16.040G, C-F-103578), 50 m, with Salix glauca in dunes. N-Greenland: Zackenberg, S of the Station, towards Zackenberg River, 74.5°N, 21°W, 10 Aug 1999, T. Borgen (TB99.264, C-F-104297), 50 m, with Dryas sp. in scrubland. E-Greenland: Jameson Land, Nerlerit Inaat/Constable Pynt, Primulaelv, 70.74°N, 22.67°W, 1 Aug 2017, H. Knudsen (HK17.020, C-F-104908), 180 m.

Distribution.

Hebeloma mesophaeum is widely distributed, but apparently uncommon in Greenland with only 11 records (2.9%). This is in contrast to the frequency in Europe, where it is very common and widely distributed ( Beker et al. 2016). From alpine and arctic Europe, it is known from the Alps, Southern Carpathians, Svalbard and Iceland. Outside Europe and Greenland, there are a few records from the Rocky Mountains (Colorado, Cripps et al. 2019) and arctic Canada ( Ohenoja and Ohenoja 2010). It is distributed from the Mediterranean area through the Temperate and Boreal zone to the Arctic and Alpine zones, being less common in the colder areas. Circumpolar, arctic-alpine, temperate, boreal and subarctic.

Habitat and ecology.

Eleven collections, six of them with Salix glauca , one with Dryas octopetala and D. integrifolia , one with Bistorta , three not reported. One record from the Rocky Mountains was also with S. glauca . The soil conditions were variable. Hebeloma mesophaeum is widespread and very versatile when it comes to hosts, including many deciduous as well as coniferous hosts ( Beker et al. 2016).

Notes.

In Beker et al. (2016), it was reported that in arctic and alpine areas there is a chance of confusion with H. marginatulum , due to the fact that sometimes H. mesophaeum , growing in such habitats, tends to have larger spores. They reported that all the ‘large-spored’ collections were from Iceland and Svalbard. In Greenland, we have also found collections with larger spores; indeed, nine of the eleven collections discussed here exhibited larger spores in a range from 10.3-11.7 × 6.4-7.1 µm, a similar range to that reported for Svalbard and Iceland. At the time, Beker et al. (2016) did consider creating a variety to address these collections but decided such a course of action was premature and that further study of this variation was required. With regard to the confusion with H. marginatulum , the strongly bicolored cap of H. mesophaeum should normally aid identification.

Figures

Figure 16. Hebeloma mesophaeum A HK 17.020, photograph H. Knudsen B distribution of cited collections C spores x 1600 and D cheilocystidia x 1000 of HK 17.020 in Melzer's reagent. Scale bars: 5 µm; microphotographs H. K. J. Beker.