The North American species of Psathyrella.

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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

[VOL. 24

Pileus cuticle of inflated cells (pedicellate cells not numerous), about 2 cells
deep, walls thin and hyaline in KOH, cell content not distinctive. Subcuticular
region hyaline in KOH, the hyphae smooth. Clamps present. No distinctive
reaction seen in any cells or tissues in mounts in Melzer's.
Type locality. Tahquamenon River, near White House Landing, Chippewa
County, Michigan.
Habit and habitat. Scattered on debris of hardwoods.
Distribution. Michigan.
Observations. This species, in the P. obtusata complex, is distinguished by its
relative lack of pigmentation and lack of a veil. The smoky content of some
cheilocystidia would indicate that in the future some basidiocarps might be found
having pale brownish gill edges.
370. Psathyrella wilsonensis A. H. Smith, sp. nov.
Pileus 1-3.5(-5) cm latus, late conicus, glaber, subspadiceus; lamellae confertae, latae, brunneolae demum triste vinaceo-brunneae; stipes 3-7 cm longus,
1.5-2.5(-3) mm crassus, albidus, sparse fibrillosus glabrescens; velum sparsum;
sporae 7.5-9.5 x 4-4.8 I; pleurocystidia 36-47x 8-13 /, fusoide ventricosa interdum flexuosa subacuta vel acuta; fibulae adsunt. Typus. Smith 52633 (MICH);
legit prope Mt. Wilson, San Juan Mountains, Colorado.
Pileus 1-3.5(-5) cm broad, obtusely conic expanding to broadly conic, rarely
convex, margin straight at first and very soon becoming naked (veil very thin),
surface moist and hygrophanous, near "buckthorn brown" when young or "snuff
brown" fading to pinkish buff. Context very thin and fragile, odor not distinctive.
Lamellae broad, close, ascending-adnate, pallid to brownish to purplish brown
and drying near "bone brown" (dark vinaceous-brown), edges even.
Stipe 3-7 cm long, 1.5-2.5(-3) mm thick, equal, fragile, hollow, whitish but
becoming generally dingy on aging and pinkish buff to pale pinkish buff as dried,
at first faintly fibrillose from the rudimentary veil, soon naked or only the very
apex slightly pruinose.
Spores 7.5-9.5 x 4-4.8 u, smooth, apex truncate from a distinct pore, shape in
face view elliptic to ovate, in profile obscurely inequilateral to subovate, color in
KOH dingy tawny, soon becoming chocolate-gray, in Melzer's reddish tawny,
wall about 0.3 [t thick.
Basidia 4-spored, 20-27x7-9 Iu, clavate, hyaline. Pleurocystidia scattered,
36-47 x 8-13 I, fusoid-ventricose with narrow flexuous or straight neck and subacute to obtuse apex, wall thin, smooth and hyaline, content of cell not distinctive.
Cheilocystidia similar to pleurocystidia but varying to shorter in the neck.
Pileus cuticle a layer of vesiculose cells 2-3 deep, the wall ochraceous to
hyaline in KOH, thin and smooth. Hyphae of the subcuticular region pale tawny
in KOH, the hyphae smooth to minutely incrusted. Clamp connections present.
Type locality. Mt. Wilson, San Juan Mountains, Colorado.
Habit and habitat. Gregarious on rotten aspen logs, August.
Distribution. Colorado.
Observations. The pleurocystidia are not those of P. obtusata or P. fulvescens.
The basidiocarps remind one of those of P. gracilis.
371. Psathyrella subterrestris A. H. Smith, sp. nov.
Pileus 1-3.5 cm latus, late convexus; glaber, subspadiceus; contextu dilute
brunneae; lamellae latae, subdistantes, avellaneae demum griseo-brunneae; stipes