Stagnicola perplexa (P.D. Orton) Redhead & A.H. Sm., Canadian Journal of Botany 64(3): 645 (1986)
Basidiospores 5.1–6.1 × 3.0–3.5 µm (145/3/3) (on average 5.6 × 3.3 µm), Q = 1.57–1.85 (Qm 1.71), V = 24.3–38.8 μm3 (Vm = 31.5 μm3), subellipsoid with a flat to depressed adaxial side in lateral view, mainly ellipsoid in front view, hilar appendix visible, smooth, wall up to 0.3–0.5 µm thick, pale yellowish in water, slightly darker at wall level, often mono- to multiguttulate, cyanophilic, inamyloid, non-dextrinoid, non-metachromatic in Cresyl blue. Basidia 18–28 × 5–8 µm, mainly tetra-spored, subcylindrical to clavate, even subcapitate, with up to 6 µm long sterigmata, content mostly smooth, at times guttulate. Hymenophoral trama regular, consisting of thin-walled, hyaline to yellowish cylindrical hyphae, 4–8 µm wide, having a parallel arrangement. Occasionally, it was observed the occurrence of crystalline particles either free or sticking to the hyphal walls. Subhymenium hardly differentiated. Cheilocystidia 25–40(–45) × 4.5–7(–8) µm, thin-walled, sub-cylindrical, at times flexuous or slightly ventricose or clavate, with a rounded, occasionally subogival or lobate apex, other times with a tapered base; edge heteromorphous. Pleurocystidia not found. Pileipellis a regular thin ixocutis, consisting of cylindrical, yellowish, thin-walled hyphae, 3–8(–10) µm wide, smooth but with occasional crystalline deposits, at times with clavate terminal elements; subcutis well differentiated, composed of short articles, 16–12(–15) µm wide, subvesicular or allantoid. Pileocystidia not found. Stipe hyphae 2–8(–10) µm wide, mostly cylindraceous, at times fusiform, parallel, often short-celled, hyaline to yellowish, thin-walled, occasionally it can be noted the presence of polymorphous, refractive, small-sized crystalline deposits. Caulocystidia present in the apical portion of the stipe, similar to the hymenial ones but more irregular in shape. Clamp-connections common everywhere. Tissues non-sarcodimitic.
Ecology and distribution: Rare. Gregarious, in autumn, saprotrophic on plant debris, in moist to wet areas, usually in acid coniferous forests among mosses. Found throughout the Northern Hemisphere (Europe and North America) and so far known from Sweden and Finland (Fries 1878 as Agaricus cidaris var. minor, Stridvall & Stridvall 1996, Gulden 2008b, 2012b), Great Britain (Scotland, Orton 1977 as Phaeocollybia perplexa; Watling & Gregory 1993), Germany (Laber & Marklund 1992), France (Broussal & Dumesny 2015, Spain (Bandala et al. 2008 as Simocybe parvispora), Moldova (Manic 2015), USA and Canada (Smith 1937, Redhead & Smith 1986). In Index Fungorum and MycoBank, Panaeolus sphinctrinus var. minor, described by Singer (1960, 1969) based on Mexican and Argentine collections, is (mistakenly) considered as a posterior synonym of A. corneipes and consequently Niveiro & Albertó (2012), Coimbra (2015) and Begerow et al. (2018) reported in their checklists S. perplexa (= P. sphinctrinus var. minor) as present in Argentine. In comparison with M. corneipes, however, P. sphinctrinus var. minor has a non-corneous stipe, lacks a tawny mycelial tomentum at stipe base.
Index Fungorum number: IF103834