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 Add this item to the list  830713 Original description
Remarks (public):This new species is the North American sister species of the recently published R. recondita, a recently introduced name for a European species that was in the past commonly referred to as R. pectinatoides Peck (Melera et al. 2016). Russula amerorecondita appears to be a common species in the United States and was probably also confused with the same R. pectinatoides Peck in the past. The microscopic features of the type of R. pectinatoides were studied by Adamčík et al. (2013) and the main differences with our new species are the more isolated spore ornamentation and the frequent mucronate pileocystidia in Peck’s species. Russula amerorecondita could also be confused with R. foetentula Peck because of the nearly identical microscopic features including spores (see Adamčík et al. 2013). However, R. foetentula was described as having an almond smell and clearly acrid taste, suggesting it might belong to the R. laurocerasi complex, whereas our species has clearly a disagreeable smell and mild taste. Microscopically, the pileocystidia of R. foetentula are narrower and apically more constricted, attenuated and often acute. This new species has a very wide distribution covering most of the eastern United States, from Ontario and Wisconsin all the way down to Florida, including specimens that are involved in associations with heterotrophic orchids (Corallorhiza, see Figure 11). 
Description type:Original description 
Description:Pileus medium-sized, 40–55 mm diam., convex and sometimes depressed; margin moderately to strongly tuberculate-striate; cuticle viscid to dry, smooth, peeling mostly to ¼ sometimes to ½ of the radius, in the centre brown to tan, light tan, grey, brown grey, sometimes very faintly orange, tan brown, towards the margin light to dark tan, orange, brown, cream. Lamellae 5–7 mm deep, close to subdistant, creamy white, off-white, whitish when not decayed, older with darker hues including orange-brown, sometimes staining slight orange-red, slight pink; lamellulae sometimes present and irregular in length, furcations present especially near the stipe; edge entire, concolorous. Stipe 20–40 × 5–15 mm, cylindrical and slightly tapering near the base, smooth, whitish, with some brown, tan or grey at the base; medulla spongy and becoming hollow; cortex ca. 2–3 mm. Context ca. 4 mm in a half of the pileus radius, first firm, then spongy, whitish, unchanging when bruised, turning pinkish with FeSO4, negative with KOH; taste slightly acrid in lamellae, sometimes almost mild; odour first like parmesan, then unpleasant, bleachy. Spore print white to pale cream (Ia–IIa). Spores (6.5–)7.1–7.6–8.1(–9.5) × (5–)5.6–6.3–6.9(–8) μm, broadly ellipsoid, Q=(1.07–)1.12–1.22–1.31(–1.5); ornamentation of moderately distant to dense [(4–)5–7 in a 3 μm diam. circle] amyloid warts, 0.4–0.6(–0.8) μm high, occasionally to frequently fused in short chains [(0–)1–3 fusions in the circle]; connected by dispersed, short, fine line connections [0–2(–3) in the circle], suprahilar spot not amyloid, but well delimited by low, small warts connected in a chain. Basidia (20–)28–34.1–40(–50) × (6–)8–9.6–11(–13) μm, clavate, 4-spored; basidiola clavate, ca. 5–7.5 μm wide. Hymenial cystidia moderately numerous, ca. 1200/mm2, 48–54.8–61.5(–72) × (6–)7–7.8–8.5(–9) μm, mainly fusiform, less frequently clavate, apically acute and often mucronate, usually with a 1–2(–4) μm long appendage, usually originating at approximately the same level as basidia, a few longer originated in the context, thin-walled; contents pale yellowish in Congo Red or in water, with dispersed inconspicuous granulations near the terminal part, staining dark red-brown in sulfovanillin. Lamellae edges fertile and similar to lamellae sides. Pileipellis orthochromatic in Cresyl Blue, not sharply delimited from the underlying context, 80–120 μm deep, two-layered, strongly gelatinized throughout; suprapellis 35–75 μm deep, epithelium-like, composed of large, up to 25–50 μm wide, sphaerical or ellipsoid and near the surface more elongated cells; hyphae often forming pyramidal structures near the pileus margin, gradually passing to the 25–45 μm deep subpellis, composed of horizontally oriented, dense, intricate, 3–8 μm wide hyphae covered by thick, glutinous coating that does not colour in Congo Red. Acid-resistant incrustations absent, but contents of cystidia and cystidiod hyphae acid-resistant (staining red after carbolfuchsin treatment). Hyphal terminations near the pileus margin scarcely branched, occasionally flexuous, thin-walled, terminal cells (15–)18–25–31.5(–44) × (3–)3.5–4.6–5.5(–6.5) μm, mainly attenuated or narrowly lageniform, occasionally cylindrical, rarely clavate, lanceolate or fusiform, often irregularly inflated near the base, apically constricted or not; subterminal cells frequently shorter and occasionally inflated, to 8.5 μm wide, rarely branched or with lateral nodules. Terminal cells of hyphae near the pileus centre similar to those near the pileus margin. Pileocystidia near the pileus margin relatively numerous, 1-celled, cylindrical, rarely lanceolate, often very long and originating in the context, a few shorter ones originating in the suprapellis, (43–)46.5–89.1–130(>150) × 4.5–5.5–6(–7) μm, apically mainly constricted or attenuated but otherwise obtuse, thin-walled; contents yellow in Congo Red and water, with dispersed granulations or locally heteromorphous-banded, weakly reactine to sulfovanillin (pale yellow-brown or pale red-brown). Pileocystidia near the pileus centre similar. Oleiferous hyphae frequent in context, with yellowish pigments. 
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