Public Description of Pluteus eos Justo & E.F. Malysheva

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Name: Pluteus eos Justo & E.F. Malysheva
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Description status: Unreviewed

General Description:

Diagnosis:—Differs from Pluteus hibbettii in the pleurocystidia with bifid hooks, partially pigmented lamellar edge and broader basidiospores.

The combination of pigmented lamellar edges near pileus margin, pleurocystidia with bifid hooks and narrowly clavate to cylindrical cheilocystidia sets Pluteus eos apart from the other members of the pouzarianus clade. Pluteus orestes also has pigmented cheilocystidia but this species has differently shaped pleurocystidia and it is restricted to mountainous habitats in western North America.

Pluteus spegazzinianus resembles P. eos in the partially pigmented lamellar edges and the presence of clamp- connections but it can be separated from P. eos in the different ornamentation of the pleurocystidia and the predominantly clavate cheilocystidia (Singer & Digilio 1952). This species is only known from Argentina. Pluteus microspermus and Pluteus concentricus may resemble P. eos in the pigmented lamellar edges but both species have smaller basidiospores (less than 6.5 μm long) and lack clamp-connections (Horak 2008). Both species are only known from New Zealand, where they grow in association with Nothofagus wood (Horak 2008).

Diagnostic Description:

Pileus 20–50 mm in diameter, hemispherical or campanulate when young, expanding to convex or plano-convex, with or without a low, broad umbo, with or without a shallow depression at center; surface smooth or innately radially fibrillose, with or without well defined squamules at center; dark brown (in the range of 5YR 3/2–3/4, 4/ 3–4/6) or gray-brown (5YR 4/1–4/2, 3/1); dry or slightly viscid when moist; margin smooth or slightly translucently striate. Lamellae crowded, free, ventricose, up to 8 mm broad, white when young, later pink, with pigmented edges but not uniformly so: dark brown in the 1/2 or 1/3 near the pileus margin and even, or white, flocculose in the part near the stipe. Stipe 30–65 × 3–15 mm, cylindrical, with slightly broad base; surface white, smooth or with longitudinal brown or gray-brown fibrils, sometimes grouped forming small squamules especially near the base. Context in stipe and pileus white. Smell indistinct. Taste indistinct. Spore print not recorded.

Basidiospores [60, 3, 3] 6.5–9.0 × 4.5–6.5 μm, avl × avw = 7.7–8.2 × 5.4–5.7 μm, Q = 1.35–1.60, avQ = 1.41–1.45, ellipsoid, sometimes ovoid or slightly constricted in the middle. Basidia 15–35 (40) × 5–15 μm, tetrasterigmate, clavate, some with median constriction. Pleurocystidia metuloid, 60–80(–100) × 12–22(–30) μm, fusiform, narrowly fusiform or narrowly utriform with 2–4 apical hooks (commonly bifid, but entire hooks also present), rarely with small lateral hooks, hyaline, with up to 4 μm thick wall, frequent all over lamellar faces. Intermediate cystidia similar to the pleurocystidia but smaller and/or with thinner walls, a few irregularly shaped, without distinct apical hooks and/or with rounded apices; without a predominant morphological type. Lamellar edge sterile. Cheilocystidia 40–70 × 12–25 μm, narrowly clavate or cylindrical, more rarely clavate or narrowly utriform, hyaline or with evenly dissolved, intracellular, brown pigment, thin-walled, crowded, forming a well- developed strip. Pileipellis a cutis, with terminal elements 85–165 × 7–17 μm, individual elements cylindrical, usually strongly tapering towards apex, mostly filled with brown intracellular pigment, with thin, smooth walls. Stipitipellis a cutis; hyphae 5–25 μm wide, cylindrical, hyaline or with brown intracellular pigment, with thin, smooth walls. Clamp-connections common and readily seen on pileipellis hyphae but not at every septum; also observed in other parts of the basidiocarp.

Habit, habitat and phenology:—Solitary or gregarious, growing on well-decayed conifer wood (e.g. Tsuga). In conifer or mixed forests. Recorded in transitional boreal/temperate or boreal areas. August–September.

Distribution:—Eurasia. Known from the Russian Far East (Primorsky Territory North America. Known from eastern North America (Newfoundland Island, New York).

Description author: Excited delirium [EXD]▼ (Request Authorship Credit)