The North American Species of Crepidotus
84. Crepidotus betulae Murr., North Amer. Flora 10: 151. 1917.
Illustration: Fig. 157.
Pileus (2) 10-24 mm broad, sessile, pure white, suborbicular or reniform, dimidiate, villose with felted hairs, glabrous toward the margin with age, margin entire. Context rather thick, fleshy.
Lamellae rounded behind, pure white, at length colored by the spores, crowded, medium broad to broad, plane, edges at times gelatinous.
Spores 6-8.5 x 4-5 µ, ellipsoid, slightly inequilateral in profile, smooth. Basidia 20-27 x 5-7 µ, 2-4-spored. Pleurocystidia none; cheilocystidia 33-65 (125) x 4-10 µ, cylindric, clavate, flask-shaped to ventricose, often tramal in origin. Gill trama subparallel, often with a brownish mediostrate and a gelatinous subhymenium, hyphae 3-7 µ broad. Pileus trama interwoven. Cuticle a gelatinous zone, 100-180 µ thick, of loosely interwoven, slender hyphae, bearing scattered, slender, colorless, erect hyphae, the innermost zone a distinct hypodermium. Clamp connections on the epicuticular hyphae and on the tomentum at the base of the pileus.
Habit, Habitat, and Distribution: On dead wood of birch, alder, beech, and other deciduous trees, New Hampshire, New York, Virginia, Tennessee, and Michigan, June-September.
Material Studied: MICHIGAN: Smith 66940,67413; NEW HAMPSHIRE: Miller 408; NEW YORK: Earle 241, type (NY),June 16, 1902; TENNESSEE: Hesler 7874.
Observations: Although Murrill (1917) described the pileus as dry, there is a distinct gelatinous, cuticular zone.