Sclerotrema griseobrunneum (K. Wells & Raitv.) Spirin & Malysheva, in Fungal Biology 121 (8): 696 (2017)
Diagnosis: Basidiocarps perennial, resupinate, first orbicular, later fusing together, leathery, up to 10 cm in widest dimension and up to 0.2 mm thick. Margin partly detaching, concolourous with or slightly paler than hymenial surface. Hymenophore soft ceraceous, smooth or covered by irregularly scattered warts, first greyish brown, later fading to pale ochraceous or light ochraceous-grey.
Basidiospores allantoid, distinctly curved, (8.4–) 9.2–14.8 (–15.3) × 2.9–4.1 (–4.3) µm (n = 60/2), L = 11.12, W = 3.39, Q = 3.28–3.32. Basidia ellipsoid-ovoid to subglobose, four-celled, (8.8–) 9.4–13.1 (–13.9) × (7.3–) 7.5–9.8 (–10.2) µm (n = 20/2). Cystidia abundant in mature specimens, hyphoid to fusiform, often sinuous, with thickened walls, 40–70 × 2.5–7 µm, sometimes with lateral outgrowths. Hyphal structure monomitic; hyphae with clamp connec tions. Subicular hyphae almost hyaline to pale brown, slightly thick-walled, subparallel, 2–4 µm in diam., CB –, some irregularly inflated up to 6 µm in diam. Tramal / subhymenial hyphae hyaline, thin-walled or with distinct walls, interwoven, partly glued together, (2.2–) 2.3–3.8 (–4.0) µm in diam. (n = 20/1), CB –. Hyphidia abundant, covering hymenial surface, richly branched, 1–1.5 µm in diam. at the apex, in intensively growing basidiocarps covered by amorphous brownish substance.
Index Fungorum number: IF 818037
Notes: Microscopic features of this species are illustrated by Raitviir & Wells (1966) and Wells & Raitviir (1977). Brown–coloured, widely effused basidiocarps, encrusted hyphidia, rather small basidia and curved, allantoid basidiospores are most important morphological characters of S. griseobrunneum. Needle-like crystals appear in 10–15 min in microscopic slides prepared in CB. Sclerotrema griseobrunneum was described from Siberia (Raitviir & Wells 1966), and it is reported here from Russian Far East and Canada. It inhabits still attached or recently fallen branches and small-sized logs of shrub-like Alnus species but rarely occurs also on Salix spp.
Figure 1. Combined phylogenetic nrITS D nrLSU topology from Maximum likelihood analysis showing main lineages within Auriculariales. The collection number (voucher or isolate) is given for each specimen. Support values (PP values in BI/BS values in ML/BS values in MP) are given above the branches. Scale bar shows expected changes per site.