Cortinarius denigratus Ammirati, Beug, Niskanen, Liimat. & O. Ceska, sp. nov.
Index Fungorum number: IF 551703, Facesoffungi number: FoF 02039, Fig. 2
Etymology – Name based on blackening of the basidiocarps on drying.
Holotype – Michael Beug 02MWB043014 (WTU)

Pileus 10 – 20 mm diam., papillate umbo, dry, Dresden Brown to Mars Yellow, edge blackens dried (in sun), minutely fibrillose, hygrophanous. Lamellae adnexed, ± distant, tan rusty. Stipe 30 – 40 mm long, 2 – 4 mm thick, ± equal, minutely fibrillose, buckthorn brown. Universal veil not recorded. Basal mycelium white. Context in stipe context ochraceous buff to yellowish tan. Odour indistinct. Macrochemical reaction (40 % KOH): all parts instantly black. Exsiccatae: pileus brown to blackish, lamellae dark dull brown to blackish, stipe brown to blackish, some white mycelium at base, context brown. Basidia 4 -spored, 9 – 10× 27 – 37 μm, clavate, hyaline, light brown or dark brown in KOH. Basidiospores 9 – 11.2 × 4.8 – 6 μm (20 spores, holotype specimens), narrowly to broadly amygdaloid, distinct apiculus, moderately to very coarsely verrucose, apex ± extended and less ornamented, slightly to somewhat moderately dextrinoid. Lamella trama hyphae hyaline, light brown or very dark brown, walls yellow refractive, heavily brown encrusted and with brown interhyphal plaques in KOH. Pileipellis in KOH: Surface layer thin, somewhat compressed, hyphae ± cylindrical, 4 – 12 μm wide, hyaline or yellowish, some encrusted. Subtending layer of cylindrical to enlarged hyphae 7 – 25 μm wide, yellow brown to orange brown, walls yellow refractive, some heavily encrusted with brown pigment. Beneath a darker brown pigmented layer of encrusted hyphae with interhyphal brown plaques, cylindrical to enlarged, mostly 7 – 22 μm wide, that gradually grade into trama hyphae. ITS sequence distinct from other species of Cortinarius subgenus Telamonia. Ecology and distribution: Found from forests of Quercus garryana and Pinus ponderosa, and Pseudotsuga menziesii and Arbutus menziesii. Producing basidiomata in spring in April. Known from British Columbia, Canada and Washington USA, Western North America.

Material examined – CANADA, British Columbia, Salt Spring Island,Mt. Tuam, 48.72° N 123.485°W, along the trail through mixed forest (Pseudotsuga, Arbutus), 19 April 2007, leg. Oluna Ceska OC155, F17227 (UBC). USA,Washington, Klickitat County, Beug Farm, N45°48′36.6″ W121°30′ 59.04″, Quercus garryana and Pinus ponderosa, 30 April 2014, leg. Michael Beug 02MWB043014 (holotype, WTU), (isotype, K(M): 200659).

Notes – Cortinarius denigratus is easily recognized since it produces fruitbodies in the spring when not that many other Cortinarius species are fruiting. Characteristic for the species are small, brown basidiomata, highly brown pigmented lamella trama hyphae, and amygdaloid, rather large spores with ± extended apex. Cortinarius denigratus is not very closely related to any of the known Telamonia species, but groups together with other small Telamonias in our phylogenetic analysis (Fig. 1).

Fig. 1 Phylogram resulting from the RAxML (Stamatakis 2014) analysis of ITS regions. Bootstrap values greater than 50 % are indicated above branches. New taxa are in blue and ex- type in bold. The tree is rooted with section Cyanites.

Fig. 2 Cortinarius denigratus (holotype) a Basidiomata b Basidiospores. Photograph a Michael Beug, b Joseph Ammirati. Scale bars: a = 10 mm, b = 10 μm.