The North American Species of Crepidotus

51. Crepidotus contortus sp. nov.

Illustrations: Figs. 13, 109.

Pileus 4-9 cm latus, conchatus demum dimidiatus, "pale olive buff,"fibrillosus. Lamellae primum subflavo-cinereae, deinde "wood brown," confertae vel densae, medio-angustae. Sporae 4.5-6 µ, globosae vel subglobosae, perraro ellipsoideae (5.5 x 4.3 µ), vel ovoideae, punctatae. Basidia 17-22 x 5-7 (8) µ tetraspora. Pleurocystidia desunt; cheilocystidia 20-40 x 7-13 µ, ramosa, contorta. Cuticula ex hyphis repentibus composita, hyphas erectas in superficie gerens. Fibulae adsunt. Specimen typicum in Herb. Univ. Mich.; lectum prope Baker Lake, Washington, Sept. 14, 1941, A. H. Smith 16956.

Pileus 4-9 (30) mm broad, attached by a broad base, conchate with an inrolled margin, expanding to dimidiate, at times flattened against the substratum but not truly resupinate, "pale olive buff," base near avellaneous at maturity, surface fibrillose, dry, margin at first fringed with fibrils. Context thin.

Lamellae extending to an area around the base, at first yellowish-gray, becoming wood brown, close or crowded, moderately narrow, edges minutely white-fimbriate.

Stipe none, or rudimentary and more or less 0.2 mm thick, on lower side of pileus.

Spores 4.5-6 µ, globose or subglobose, more rarely short-ellipsoid, about 5.5-4.3 µ, occasionally ovoid, punctate, dingy yellow-brown in 2% KOH, wall slightly thickened, many spores collapsing in KOH and in chloral hydrate. Basidia 17-22 x 5-7 (8) µ 4-spored. Pleurocystidia none; cheilocystidia 20-40 x 7-13 µ irregular, forked or branched, often greatly contorted by knob-like outgrowths. Gill trama subparallel, hyphae 3-5 µ broad. Pileus trama interwoven. Cuticle of repent hyphae, bearing erect, colorless hyphae 3-6 µ broad. Clamp connections present on the epicuticular hyphae.

Habit, Habitat, and Distribution: On twigs of vine maple (Acer circinatum Pursh) and Populus, Washington, May and September.

Material Studied: WASHINGTON: Smith 16956 (type, from Baker Lake, Sept. 14, 1941, 13558).

Observations: The strikingly contorted cheilocystidia, the small, "pale olive buff" pileus, and yellowish-gray gills characterize it.