Pseudobaeospora celluloderma Bas

Pseudobaeospora celluloderma Bas, Persoonia 18 (1): 119 (2002) Fig. 12 Holotype. ENGLAND • Surrey, Mickleham Downs, 19 June 1991, leg. A. Henrici (K (M) 17188). Selected iconography. Karasch (2004: 34 Abb. 6). Selected descriptions. Bas (2003: 173–174), Adamčík et al. (2007: 370–372). Description. Spores (3.3 –) 3.7–4.0 – 4.4 (– 5.0) × (2.7 –) 2.9–3.2 – 3.5 (– 4.4) μm (64 / 2 / 2), Q = (1.00 –) 1.16–1.28 – 1.41 (– 1.61), V = (14.1 –) 15.9–21.5 – 27.2 (– 50.1) μm 3, globose to subglobose or broadly ellipsoid, walls up to 0.8 µm thick, dextrinoid at maturity, smooth, colorless in L 4; hilar appendix prominent, 0.8–1 µm long. Basidia 16 × 4 µm, tetrasporic, clavate, sterigmata up to 2.5 µm long. Hymenophoral trama regular to subregular, composed of globose to subglobose, broadly cylindrical, up to 22 µm wide hyphae, colorless in L 4. Cheilocystidia 23–25 × 5–7 µm, thin-walled, poorly differentiated and similar to basidioles. Pleurocystidia absent. Pileipellis: suprapellis cellulodermic / epithelioid, composed of slightly gelatinized, smooth, globose to subglobose, up to 24 × 22 µm elements; subpellis like suprapellis structure but with 21 × 13 µm elements, with rare cylindraceous hyphae; pigments greenish, intracellular. Stipitipellis consisting of up to 4 µm wide, multiseptate, closely packed, longitudinal hyphae. Stipititrama like stipitipellis structure but with up to 12 µm wide hyphae. Caulocystidia 12–22 × 2–7 µm, numerous at stipe apex, single or in small clusters, scattered towards the stipe base, often multiseptate with terminal elements cylindrical to broadly clavate. Clamp-connections rare, scattered. Specimen examined: SLOVAKIA, Vihorlatské vrchy Mts., ca. 1.5 km SW of the church, old pastures, Strihovce village, terrestrial, on flysh, 18 April 2003, leg. V. Kučera (SAV-F: 3516). SWEDEN, Medelpad, Borgsjö, öster om Östby, Örtrik granskog (Medelpad, Borgsjö, east of Östby, Örtrik spruce forest), 3 September 1991, leg. L. Andersson (UPS-F: 623041) (as Pseudobaeospora pillodii). Notes. Pseudobaeospora celluloderma is a well characterized species circumscribed by its minute and slender mycenoid basidiomes which are brightly purple to reddish violet when moist (reminding Laccaria amethystina Cooke), sometimes greyish vinaceous coloured; strongly translucently striate pileus when moist; lamellae concolorous with pileus; pileus surface in KOH pale brownish to pale pinkish-greyish, clamp-connections present (sometimes as pseudoclamps, Bas 2003); cheilocystidia absent or basidiole-like, and an irregular hymenidermic pileipellis (Bas 2002, 2003; Adamčík et al. 2007; Kalinina et al. 2020). It was reported in Europe from Austria, Denmark, England, Finland, France, Germany, Slovakia, Sweden, and Russia (Bas 2002, 2003; Karasch 2004; Courtecuisse and Lécuru 2006; Adamčík et al. 2007; Læssøe 2008, 2012; Hausknecht et al. 2012; Kalinina et al. 2020). The sequences from two North American collections named P. celluloderma (KU 058501, USA North Carolina, ECV 5550 / TENN 067659) and Pseudobaeospora sp. (KU 058500, USA, Tennessee TENN 070699 / CCB 143666) (Figs 2, 3) are weakly supported as sisters related to the two European collections we have sequenced and studied, and probably represent one or two distinct undescribed taxa.