The North American Species of Crepidotus

113. Crepidotus obscurus sp. nov.

Illustrations: Figs. 187a, b.

Pileus 5-30 mm latus, albus deinde brunnaceus, fibrillosus, margine lobatus. Lamellae latae, confertae, albae deinde brunneae. Pseudostipes 2-3 mm x 0.5-0.7 mm, albus, centro aberrans. Sporae 7-9 x 4.5-5.5 µ, ellipsoideae, rugoso-verrucosae. Basidia 22-26 x 7-8 µ, tetraspora. Pleurocystidia desunt; cheilocystidia 24-38 x 4-8 µ, clavata, cylindrica, ventricosa, vel 33-55 x 10-28 µ clavata, napiformia vel sphaeropedunculata. Cuticula ex hyphis repentibus composita, hyphas erectas gerens. Fibulatae adsunt. Specimen typicum in Herb. Univ. Mich.; lectum prope Ann Arbor, Mich., Sept. 15, 1938, A. H. Smith 10963.

Pileus 5-30 mm broad, at first pure white and white-fibrillose or pubescent throughout, finally subglabrescent near the margin, at maturity sordid brownish, applanate, large pileus variously wavy or lobed, at times almost orbicular. Context thin, soft, whitish; odor and taste mild.

Lamellae broad, close, adnate-to or free from the stipe, white then sordid brown.

Stipe a pseudostipe, 2-3 mm long, 0.5-0.7 mm thick, white, appearing eccentric, not attached to substratum.

Spores 7-9 x 4.5-5.5 µ, ellipsoid, obscurely wrinkled-verrucose, thick-walled. Basidia 22-26 x 7-8 µ, 4-spored. Pleurocystidia none; cheilocystidia of two general types: (a) clavate, ventricose, cylindric, 24-38 x 4-8 µ; (b) broadly clavate, napiform to sphaero-pedunculate, 33-55 x 10-28 µ. Gill trama slightly interwoven to subparallel, hyphae 7-10 (14) µ broad, of relatively short cells. Pileus trama interwoven. Cuticle of repent hyphae, bearing scattered or gregarious, erect hyphae, which may be branched. Clamp connections present.

Habit, Habitat, and Distribution: On basswood, Michigan, September.

Material Studied: MICHIGAN: Smith 10963, type, from Ann Arbor, Sept. 15, 1938.

Observations: The cheilocystidia are strikingly different in shape from those of C. subverrucisporus, and the spores less conspicuously wrinkled-verrucose.