Hygrophorus viridiflavidus L. Fan & Y. X. Zhang 2023, sp. nov

Hygrophorus viridiflavidus L. Fan & Y.X. Zhang sp. nov. (Fig. 2, 3) MycoBank:— MB846250 Diagnosis: differs from the other species of subgenus Colorati section Limacini in its medium-sized basidiomata, lamellae partially turning yellowish green when bruised, shorter and narrower basidia 35.0–46.5×8.0–10.5 μm, cystidioid elements absent, and longer and narrower basidiopores (8.5–)9.0–10.5(–11.0) × (4.5–)4.8–5.8(–6.0) μm. Etymology: viridiflavidus, viridi -, meaning green, flavidus, meaning yellowish, referring to the lamellae gradually turning light yellowish green when bruised. Holotype: CHINA. Shanxi Province, Qinshui County, Lishan Mountains, Zhongcun Forest Farm, on the ground in forest of Quercus spp., 112°1’27’’E, 35°29’7’’N, elev. 1,680 m, 24 August 2020, collected by H. Liu LH 1116 (BJTC FM978, GenBank Acc. No.: ITS = OP699731, nrLSU = OP699736, tef1-α = OP723351). Description: Basidiomata medium-sized, firm, fleshy, with dark greenish tone. Pileus 41–57(–98) mm, hemispherical or obtusely conical with strongly involute margin at first, then expanded to almost flat with prominent obtuse umbo, first rather dark yellow (#917625) or olivaceous brown (#676700) with dark greyish (#1b1b00) to blackish brown (#424200) centre, then paler especially in marginal zone towards light greyish (#786e4c) or olivaceous brown (#676700), mostly with olivaceous (#9b8957) or dark greenish (#4e4e00) tinge, centre always much darker, very strongly glutinous. Lamellae adnate to subdecurrent, thick and waxy, white (#ffffff), partly gradually turning light yellowish green (#cccc00) to drying cream (#ffeb07) when bruised. Stipe 38–79 × 10–23 mm, cylindro-clavate to ventricose, often flexuous or bent and tapering-rooting towards the base, connected with margin of cap by a glutinous hyaline veil when young, then veil burst and disappear with maturity, with an unconspicuous annular zone at the apex, pale yellowish white (#ffffd6), smooth or with white (#ffffff) floccules above the annular zone, covered by successive bands of thickly glutinous, dark brown (#856731) or greyish brown (#433419) flocci below, drying greybrown (#686042). Context thick, pure white (#ffffff), in stem also white or slightly yellowish at base. Smell indistinct. Taste not recorded. Spore deposit white. Basidiopores ellipsoid to broadly ellipsoid or somewhat ovoid, measuring (8.5–)9.0–10.5(–11.0) × (4.5–)4.8–5.8(– 6.0) μm; Q =1.58–2; Qm =1.79±0.11, with an oblique hilar appendage 1–2 μm long; inamyloid, hyaline and smooth or microguttulate in water, appearing monoguttulate in KOH. Basidia 2-spored or 4-spored, clavate, 35.0–46.5 × 8.0–10.5 μm, some with oily refractive content in KOH; sterigmata 3.5–5.5 μm long. Cystidioid elements absent. Hymenophoral trama divergent, comprised of cylindrical, interwoven, branched hyphae 3–13 μm wide. Pileipellis an ixotrichoderm composed of thick-walled, hyaline or brown-pigmented interwoven hyphae 2.5–4 μm wide, hyaline or with olive green intracellular pigment, sparsely branching and embedded in a gelatinous matrix; incrustations or extracellular pigment not seen. Subpellis composed of more or less parallel hyphae up to 9 μm wide. Stipitipellis an ixotrichoderm, made up of branched hyphae 3–5 μm wide, with yellowish brown intracellular pigment; terminal elements rounded to attenuated, not enlarged. Stipititrama composed of densely packed, more or less parallelly arranged, subhyaline hyphae up to 9 μm wide. Floccules at the apex composed of compact fascicles of branched hyphae with cylindrical or slender clavate terminal elements 37–74 × 5–9 μm. Clamp connections present in all tissues. Ecology & Distribution: associated with Quercus spp. in elevation 1,680 m, only known from Shanxi Province, northern China. Additional specimens examined (paratypes): CHINA. Shanxi Province, Qinshui County, Lishan Mountains, Zhongcun Forest Farm, on the ground in forest of Quercus spp., 112°1’21’’E, 35°29’3’’N, elev. 1,680 m, 24 August 2020, collected by H. Liu LH 1139 (BJTC FM999, GenBank Acc. No.: ITS = OP699730, nrLSU = OP738418, tef1-α = OP723352).
Published as part of Zhang, Yu-Xin, Mao, Ning & Fan, Li, 2023, Hygrophorus viridiflavidus sp. nov. (Hygrophoraceae, Agaricales), from North China, pp. 187-197 in Phytotaxa 579 (3) on pages 191-192, DOI: 10.11646/phytotaxa.579.3.4, http://zenodo.org/record/7550376