The North American species of Psathyrella.

1972]

PSATHYRELLA

117

obscurely inequilateral, color in KOH very quickly dark chocolate-brown but
becoming violaceous-fuscous on standing, reddish tawny in Melzer's, wall about
0.2 /, thick.
Basidia 4-spored, clavate, 14-18 x 5-8 pu, hyaline. Pleurocystidia 34-46 X
9-15,, fusoid-ventricose with broadly rounded to obtuse apex (in age), neck in
some scarcely developed, wall thin, smooth and hyaline, content of cells not
distinctive. Cheilocystidia clavate to ellipsoid and up to 18 ML broad, hyaline, some
cells similar to pleurocystidia also present. Hyphae of subcuticular zone in pileus
vinaceous-cinnamon in KOH, walls incrusted. Cuticle of pileus a layer of vesiculose hyaline to cinnamon colored cells 2-3 deep (if colored soon fading). Clamp
connections present.
Type locality. Colonial Point, Burt Lake, Cheboygan County, Michigan.
Habit and habitat. Subcespitose on a birch (Betula sp.) log, September.
Distribution. Known only from the type locality.
Observations. The spores are slightly larger than in P. hydrophila, and the
differences in the veil are striking. It appears to be closest to P. septentrionalis
in veil features but has smaller spores. In a collection by Hesler (no. 22988),
which is tentatively placed here, there occur hyaline refractive particles of dried
mucilaginous material on or around the apex of the pleurocystidia.
75. Psathyrella avellaneifolia A. H. Smith, sp. nov.
Pileus 2-3.5 cm latus demum subplanus, fibrillosus, glabrescens, ad marginem
appendiculatus, subspadiceus; lamellae circa 3 mm latae, confertae, avellaneae,
demum ligno-brunneae (pallide fuscae); stipes 4-5 cm longus, 3-4 mm crassus,
fragilis deorsum sparse fibrillosus tactu sordide avellaneus; sporae 6.2-7.5 x
3.1-3.6 x 3.6-4.5 yt; pleurocystidia 36-54 x10-15 u, fusoidea, acuta, in "KOH"
vinaceo-avellanea; fibulae adsunt. Typus. Smith 21463 (MICH); legit prope
Burt Lake, Michigan.
var. avellaneifolia
Illust. Text Figs. 189, 190.
Pileus 2-3.5 cm broad, obtuse when young, becoming nearly plane with an
obtuse umbo or umbo obsolete, surface at first hairy-fibrillose from the remains
of a thin outer veil, soon glabrous or nearly so on the disc, the fibrils near the
margin appressed into fascicles, margin appendiculate at first, color evenly
"Prout's brown" or with a slightly more yellowish margin, hygrophanous, when
faded near "cinnamon-buff." Context very watery and fragile, odor and taste not
distinctive.
Lamellae depressed adnate, moderately broad, (about 3 mm), 2-3 tiers of
lamellulae, the third often rudimentary, somewhat ventricose in age, pale avellaneous when young, near wood brown at maturity, edges even.
Stipe 4-5 cm long, 3-4 mm thick, equal, hollow, fragile, white, striate near
apex, scurfy below and toward the base more or less fibrillose, finally becoming
glabrous, becoming sordid avellaneous at base where handled-especially in age.
Spore deposit near "cinnamon-drab." Spores 6.2-7.5x 3.1-3.6 x 3.6-4.5 v,
slightly flattened, smooth, apical pore present but not conspicuous, shape in face
view ovate to obscurely angular-ovate, some obscurely truncated at the base, in
profile view obscurely bean-shaped to obscurely inequilateral, color in KOH cocoacolor slowly clouded chocolate-gray, in Melzer's tawny, wall about 0.2 v thick.