Mycetinis subalpinus (P.-A. Moreau) R.H. Petersen, comb. nov.

Petersen, Ronald H. & Hughes, Karen W., 2017, An investigation on Mycetinis (Euagarics, Basidiomycota), MycoKeys 24, pp. 1-138 : 58-59

12. Mycetinis subalpinus (P.-A. Moreau) R.H. Petersen, comb. nov.

Marasmius subalpinus Basionym. P.-A. Moreau 2007. Bull. Mycol. Bot. Dauphiné-Savoie 186: 50.

Holotype.

Austria, Tirol, Obergurgl, N46°52'13", E11°01'37", 28.VIII.2006, coll. P.-A. Moreau, no. 05082708 (LIP, isotype ZT).

Diagnosis.

1) Basidiomata diminutive (pileus 3-10 mm broad; stipe 20-30 × 0.5-1 mm); 2) associated with Rhododendron ferrugineum twigs and leaf litter; 3) strong odor of garlic from fresh material but dissipating in drying; 4) adult pileus pallid rosy, shallowly sulcate-striate; 5) spores 9.5-11.8 × 5-6.2 µm, subamygdaliform, somewhat tapered proximally; 6) stipe subinsititious or minutely wooly at base.

The following description is a translation and rearrangement of the protolog description by Moreau (2007).

Description.

Basidiomata diminutive. Pileus 3-10 mm broad, strongly convex when young becoming convex, often subtly broadly umbonate, eventually plane to everted, weakly subhygrophanous, smooth, a little glistening, entirely dark reddish in very juvenile specimens, becoming brown-red, rapidly paling to dull ochraceous yellow with age, with central umbo remaining dark reddish, uniformly brownish when dried; margin entire to shallowly sulcate-striate, paler than disc. Lamellae distant, thickish, ventricose, adnate, attached to a loose or clasping pseudocollarium, total lamellae 20-28, through lamellae 10-12, whitish then pale cream in age, with scattered dark reddish punctations; lamellulae in 1(-2) ranks. Spores deposit not obtained. Stipe 20-30 × 0.5-1 mm, terete, equal, insititious to subinsitititious, flocculose at apex and occasionally to midsection, somber reddish when young, in age assuming an ochre shade, yellow-red mycelium apparent on the stipe apex. Rhizomorphs not visible. Flesh pliant, reviving. Odor very powerful of garlic ( Allium sativum ), dissipating on drying but regenerating on rehydration; taste alliaceous, sweet.

Habitat and phenology.

Known from only few specimens; apparently associated with dead twigs, leaves and litter of Rhododendron ferrugineum ; approximately tree-line in Rhododendron belt in mountains of central Europe (Austria, France, Switzerland); mid-summer.

Pileipellis an irregular hymeniform layer about 80 µm thick, of hyphal termini 18-55 × 6-22 µm, arising from subterminal elements, irregularly clavate to obpyriform, thin- to thick-walled (wall -1 µm thick, yellow brown), entire to mostly forming digitate diverticula, mixed with shorter, non-emergent, cylindrical articles; diverticula 3-6 µm long. Hypodermium filamentous, hardly differentiated, of slender hyphae (2-4 µm diam), smooth or with pigment incrustation in hardly separable scabs. Pileus trama dextrinoid, of mixed hyphae, more regular in hypolamella, with slender cylindrical hyphae (-3.5-10 µm diam), smooth or with various granular pigment deposits here and there. Lamellar trama regular, dextrinoid, of slender, clamped hyphae (3-3.5 µm diam), parallel, hyaline. Subhymenium filamentous, dense, arranged in a layer. Pleurocystidia fusiform, with attenuate apex before maturity, clamped (see illustration with basidia; Moreau 2007). Basidioles clavate, clamped; basidia 38-45 × 8.5-9.5 µm, cylindro-clavate, (2-)4-sterigmate, clamped; sterigmata short. Basidiospores (9.0)9.5-11.8(12) × 5.0-6.2 µm [Q = (1.60)1.75-2.03(2.20)], fusiform-amygdaliform to subcylindrical, generally more or less obtuse distally, smooth, non-dextrinoid, not cyanophilous; contents often with a large central guttule. Lamellar edge sterile; cheilocystidia 22-40 × 6-10 µm, numerous but short and hardly emergent, cylindrical, lobed with irregularly digitate diverticula, mixed with clavate basidioles with yellowish content. Stipe cortex of slender hyphae (3-5 µm diam), with fine, yellow, strongly localized incrustations; medulla dextrinoid; caulocystidia, 18-80 × 4-11 µm, hyaline, gnarled, cylindrical or clavate, isolated or in compact bouquets.

Commentary.

Moreau (2007) compared M. subalpinus to M. kallioneus and M. scorodonius var. virgultorum (here at species rank), now accepted as members of Mycetinis , and suggested (pers. comm.) such a transfer for M. subalpinus . The coarsely hymeniform pileipellis of M. subalpinus , composed of inflated, thick-walled hyphal termini and broom cell-like, branched pileocystidia, is also typical of Mycetinis . Macroscopically, basidiome size and stature, with reddish coloration, thick, ventricose lamellae attached to a clasping pseudocollarium also point toward Mycetinis . Association with Rhododendron is similar to substrate preference of M. opacus , which also exhibits branched pileocystidia, but similarities end with these limited characters. Basidiomatal size and stature are reminiscent of My. curraniae , My. olidus and My. cinnamomeus .