Psathyrella tintinnabula J.Q. Yan
Mycobank MB 828476
Pileus 5.0–12 mm, bell-shaped to conical, with a clearly obtuse umbo, brown (7D8-7E7), paler brown (7C5-7C7) towards the margin, striate up to 3/4 from margin at maturity. Veil well developed in the early stages, white (7A1-7B1), fibrillose, gradually disappearing in later stages. Context very thin and very fragile, about 1.5 mm at center, hygrophanous, same color as pileus. Lamellae about 1.5–2.0 mm broad, moderately distant, thin, adnate, initially dirty white (7A1-7A2), becoming dark brown (7E7-7E8) as spores mature. Stipe 25–40 mm long, 1.0–1.5 mm thick, cylindrical, hollow, equal, fragile, white(7A1) or dirty white with the slightly brown tinge(7C4-7C5), covered with white or greyish white (7A1-7B1) fibrils that fall off easily. Basidiospores 6.8–7.8(8.3) × 4.3–5.1 (5.6) μm, Q=1.4–1.7 (2.0), ellipsoid to slightly oblong-ellipsoid, in profile flattened on one side, red-brown in water, dark brown in 5% KOH, inamyloid, smooth, germ pore distinct, 1.0–1.5 μm in diam. Basidia 15–20 × 7.5–8.8 μm, clavate to shortly clavate, hyaline, 4-spored. Pleurocystidia 38–51 × 7.5–11 μm, numerous, fusiform, rarely lageniform, with subacute apex, and rarely adhering deposits at the apex. Cheilocystidia 23–30 × 7.5–10 (13) μm, abundant, similar to pleurocystidia, mixed with the rare pyriform cells. Lamellar trama irregular, hyphae, up to 8 μm. Pileipellis consisted of 1–2 cells deep layer of the subglobose cell, 20–33 μm broad. Veil composed of hyphae. Clamps present in all tissue.
Habit and habitat: Solitary to scattered on humus in mixed forests of Quercus spp., Abies spp. and Picea spp.
Additional Material examined: CHINA. Yunnan Province: Potatso National Park, Shangri-la County, Diqing Tibetan Autonomous Prefecture, 15 Aug 2018, Jun-Qing Yan, Yu-Peng Ge, HMLD2497, Genbank No. MK123930 (ITS).
Notes: Based on the basidiospores that rarely exceed 7.5 μm in length and the thin-walled pleurocystidia, it can be classified in section hydrophilae in Kits van Waveren’s infrageneric classification system (1985; 1987). However, there are no other species in this section that matches the combination of characters of the new species. The closely related P. umbrina Kits van Wav. differs in having mucronate pleurocystidia and basidiospores with indistinct germ pore (Kits van Waveren 1982). Psathyrella pseudocasca (Romagn.) Kits van Wav. resembles P. tintinnabula in the characteristics of cystidia, but it has bigger basidiomata with a pileus up to 70 mm in diam. and a robust stipe up to 8.0 mm thick, and spores that are at least partially rough(Kits van Waveren 1982; Kits van Waveren 1987; Örstadius & Kundsen 2012). Some other species with the same size of spores, belonging to the subsection, can be separated as follows: the germ pores of basidiospores of P. cortinarioides [synonyms P. frustulenta (Fr.) A.H. Sm.] and P. atomatoides (synonyms P. rannochii Kits van Wav.) are either absent or indistinct (Orton 1960; Smith 1972; Örstadius & Kundsen 2012;); P. mucrocystis A.H. Sm. has mucronate pleurocystidia and basidiospores with indistinct germ pore (Smith 1972); P. obtusata (Pers.) A.H. Sm. has mucronate cheilocystidia (Örstadius & Kundsen 2012); P. pertinax (Fr.) Örstadius [synonyms P. chondroderma (Berk. & Broome) A.H. Sm.] has robust basidiomata and often broadly truncate basidiospores (Örstadius 2007; Örstadius & Kundsen 2012).
Fig. 1 Bayesian and Maximum Likelihood tree inferred from partial ITS sequence data (BPP ≥0.95, Bootstrap ≥75 are indicated). The tree is rooted with Coprinellus christianopolitanusÖrstadius & E. Larss. ● indicates newly described species.