The North American species of Psathyrella.

1972]

PSATHYRELLA

381

Habit and habitat. Densely cespitose around dying aspens and around stumps,
August.
Distribution. Colorado, New Mexico, Wyoming.
Observations. This species is related to P. multipedata but differs in slightly
larger spores and smaller cheilocystidia as well as in lacking a pseudorhiza. The
association was clearly with aspen.
Material examined. Colorado: Smith 51783 (Type), 51784, 51785, 51786,
51787, 51788, 51789, 51790, 51791, 51792, 51793, 51794, 51929, 51941, 51944,
51945, 52231, 52331, 52353, 52439, 52645, 52646. New Mexico: Barrows 528,
1808, 2005, 2098, 40-1968. Wyoming: Solheim 3334, 3335, 3338, 4867.
355. Psathyrella microsperma (Peck) A. H. Smith, Contr. Univ. Mich. Herb. 5:
33. 1941.
Psathyra microsperma Peck, Bull. Torrey Club. 26: 68. 1899.
Atylospora microsperma (Pk.) Murrill, Mycologia 14: 264. 1922.
Illust. P1. 86, fig. a; Text Figs. 793, 794.
Pileus 1-2.5 cm broad, ovoid to obtuse or nearly hemispheric, becoming subcampanulate to broadly convex, even, hygrophanous, brown when moist, paler
when dry, slightly floccose when young. Context thin, brownish, fading to pallid.
Lamellae thin, close, adnate, brown.
Stipe 2.5-3 cm long, 2-3 mm thick, equal, hollow, white-fibrillose but soon
glabrescent, white or whitish, fragile.
Spores 6.5-8x4-4.5 p, smooth, apical pore indistinct and apex not truncate,
shape in face view broadly subfusoid or more ovate (more pointed at base than
the apex), varying to subelliptic, in profile obscurely inequilateral or with the
ventral line nearly straight and the dorsal line convex (in optical sections), color
in KOH at first dull bister (dingy yellow-brown) slowly changing to a dingy
cocoa-color and finally more chocolate-brown, in Melzer's reddish tawny to bay,
wall about 0.3, thick.
Basidia 4-spored, 12-14x6-8 u/, short and obese, hyaline in KOH. Pleurocystidia and cheilocystidia similar 26-37x 10-13 J/, fusoid-ventricose, the apex
acute to subacute (almost needle-like in some), the wall up to within about 10,
of the apex slightly thickened and highly refractive in many, the thin-walled
apical portion slow to revive, hyaline in KOH and content not distinctive.
Caulocystidia not found on the fragment of the stipe (from the type) available
for examination. Large laticiferous elements present in the stipe cortex.
Pileus cuticle of vesiculose cells more than one cell deep, the walls smooth,
thin and hyaline to yellowish in KOH. Hyphae of the subcutis rusty brown in
KOH. Clamps present.
Type locality. Ohio.
Habit and habitat. Cespitose about old stumps.
Distribution. Michigan, Ohio, Wyoming.
Observations. The clusters seen to date were not as large as in P. ophirensis.
The two are very close but the feature of the truncate vs. nontruncate spore apex
appears to distinguish them.
Material examined. Michigan: Smith 34257. Ohio: (Type). Wyoming:
Arenberg 24.