Entoloma mengsongense A.N. Ediriweera, Karun., J.C. Xu, K.D. Hyde and P.E. Mortimer
MycoBank number: MB 815072; Facesoffungi number: FoF 02080.
Pileus 3.5–5 cm diam., conical when young, planoconcave when mature, with an umbo; surface dry, fibrillose all over the surface, more so at the center, yellowish-brown (5E8); surface yellowish–brown (5E8) because of the fibrillose pileipellis, below the pileipellis sky blue becoming greenish-blue (25E7) when drying or mature, and staining yellow–blue-greenish (25A4) on bruising or cut. Lamellae adnexed, moderately crowded, with lamellulae of four lengths, ventricose, sky blue, turning yellowish-green or greenish-blue (25A4) on handling; margin smooth. Stipe 6.5–9 cm × 6–7 mm, confluent with the pileus, central, brittle, cylindrical, solid; surface, fibrillose as the pileus when young; concolorous with the pileus when young, becoming sky blue (21A6) when mature, with cottony white mycelium at the base. Context white and thin, turns yellowish-green or greenish-blue on bruising or drying. Odor peculiar and distinct. Taste was not tested. Basidiospores 4–8 × 4–6 µm, µl (mean length of basidiospores) = 5.33 µm, µw (mean breadth of basidiospores) = 5.14 µm, σl (standard deviation of length) = 1.45, σw (standard deviation of breadth) = 0.6, Q = 0.68–1.49, Qm = 1.01, cuboid–quadrate, having four angles that are regular to irregular in profile or side views, with a stramineous wall that is slightly thickened. Basidia 40–60 × 9–14 µm, mostly clavate, sometimes obclavate, 4-spored, occasionally 1-, 2-, or 3-spored; sterigmata up to 5 µm long. Cheilocystidia 35–40 × 9–12 µm, clavate, thin-walled, hyaline. Hymenophoral trama subregular; hyphae 3–15 µm wide, hyaline and thin-walled; subhymenium poorly developed. Pileal trama parallel–interwoven; hyphae similar to those of lamellar trama. Pileipellis a cutis, hyphae 2–10 µm diam., thin-walled, pale yellowish. Stipitipellis a disrupted cutis; hyphae 1–8 µm broad, thin-walled, hyaline, forming ascending or erect bundles of mostly clavate or occasionally cylindrical, 7–8.5 µm broad hyphal ends at the tip. Clamp connections present in all tissues. (Figs 1–3)
Habitat: Gregarious on soil as small groups, so far only known from the type locality in China.
Diagnosis: this species is characterized by a fibrillose, sky blue to greenish-blue pileus; cuboid–quadrate, 4–8 × 4–6 µm sized basidiospores; clavate, 40–60 × 9–14 µm sized basidia and hyaline, clavate, 35–40 × 9–12 µm sized cheilocystidia.
Material examined: CHINA. Yunnan Province: Xishuangbanna, Mengsong Village, UTM N2379744.485281, UTM E653217. 753714, alt. 1600 m, on soil associated with mosses, 12 June 2012, Samantha C. Karunarathna (HKAS 90774, holotype). CHINA. Yunnan Province: Xishuangbanna, Mengsong Village, UTM N2379744.485281, UTM E653217. 753714, alt. 1600 m, on soil with decaying leaf litter, 15 July 2012, Samantha C. Karunarathna (HKAS 90775, paratype)
Notes: Although E. mengsongense is phylogenetically closely related to E. virescens and E. hochstetteri, it is morphologically distinct. Entoloma virescens differs from E. mengsongense in having a wavy margin to the pileus, larger (10.5–12.5 × 10.5–12 µm) cuboid basidiospores, 30–52 × 10–17 µm size basidia, 30–62 × 12–16 µm size cylindro-clavate cheilocystidia (Alves and do Nascimento, 2012). Entoloma hochstetteri differs from our new species in having an indigo–blue pileus, 9.9–13.2 × 11.8–13.2 µm size basidiospores, 35–44 × 9–13 µm size basidia; and 40–60 × 8–14 µm, fusoid cheilocystidia. The cuboid basidiospores, long basidia, conic-campanulate pileus with appressed fibrils, and abundant clamp connections place our new species E. mengsongense in Entoloma subgenus Inocephalus (Noordel.) P.D. Orton. All the morphologically similar blue Entoloma species are compared with Entoloma mengsongense.