Albomagister parviniveus Matheny, Sanchez-Garcia & Vellinga 2024, sp. nov.

Albomagister parviniveus Matheny, Sánchez-García & Vellinga, sp. nov. (Figs. 6J–6K) MYCOBANK: MB851402. TYPE: USA, Tennessee, Sevier County, Great Smoky Mountains National Park, Cherokee Orchard, last turn-off before Rainbow Falls (36.1328 -83.8144), on acidic soil in cove hardwood forest near Tsuga canadensis, Pinus, Quercus, 31 August 2013, E.C. Vellinga MSG144 (holotype designated here, TENN-F-071074). DIAGNOSIS: Differs from other Albomagister by the absence of pleurocystidia, small basidiome size, and occurrence in eastern North America. Differs from A. virgineus by the slightly smaller spores, none of which are dextrinoid, and occurrence in acidic cove hardwood forests of eastern North America. Habit small, mycenoid to inocyboid. Pileus up to 15 mm wide, convex, whitish, smooth, dry. Lamellae adnexed, close, whitish. Stipe 20 × 2 mm, slightly enlarged at the base; surface dry, fibrillose, off-white. Basidiospores 5– 5.3 –6(– 6.5) × 4– 4.7 –5.5 µm, Q 1.08– 1.16 –1.28 (n = 40/1), subglobose to broadly elliptic, with a guttule, hyaline, inamyloid and nondextrinoid, with a distinct apiculus, white in deposit. Basidia 24–29 × 6–8 µm, 4-spored, narrowly clavate to subcylindric, hyaline. Pleurocystidia absent. Cheilocystidia 24– 52 × 5–7.5 µm, cylindric to narrowly utriform, at times narrowly clavate-flexuous, very long pedicellate, forming a sterile lamellar edge. Pileipellis hyphae slightly interwoven with some tips projecting upwards; terminal hyphae 55–98 × 6– 9 µm, these narrowly cylindric to somewhat clavate-fusiform, hyaline, apices generally obtuse (rarely rostrate). Stipitipellis with scattered terminal cells 15–39 × 6–8 µm, these cylindric to clavate, smooth, thin-walled, hyaline. Clamp connections present in all tissues. TAXONOMIC NOTES: Albomagister parviniveus is the same as “undet small white” in Sánchez-García et al. (2014, 2017). The species is distinguished from other American Albomagister most notably by the very small basidiomes and absence of pleurocystidia. We have only observed this species twice over a span of 15 years, but on both occasions at Cherokee Orchard in the Great Smoky Mountains National Park. The species is sister to the European A. virgineus, which also lacks pleurocystidia; however, it differs from A. parviniveus by the slightly larger spores with occasional dextrinoid walls and occurrence in a boxwood (Buxus) habitat in France. ETYMOLOGY: parviniveus (Latin), small and white, in reference to the small white basidiomes. DISTRIBUTION AND ECOLOGY: Albomagister parviniveus is known only from the type locality in the Great Smoky Mountains National Park where it has been collected in two different years. This species occurs singly on acidic soils in cove hardwood forests near Tsuga, Quercus, Betula, and Pinus. Basidiomes were observed in August. ADDITIONAL SPECIMENS EXAMINED: USA, Tennessee, Sevier County, Great Smoky Mountains National Park, Cherokee Orchard Loop Road (35.6758, −83.4861), on ground in cove hardwood forest near Tsuga canadensis, Quercus, Betula, Pinus, 6 August 2009, M.B. Pilkington MBP6.VIII.09 (TENN-F-064359).