The North American species of Psathyrella.

1972]

PSATHYRELLA

321

Lamellae close, narrow, adnate, near avellaneous becoming "benzo brown"
(violaceous-fuscous), and drying near fuscous, edges even.
Stipe 5-8 cm long, 2-3.5 mm thick, equal or nearly so, fragile, white and
undulating, drying whitish, fibrillose from veil remnants but becoming glabrous,
apex slightly pruinose, shining and not discolored in age.
Spores 9-10.5 x 5-6.3 /J, smooth, apical pore small but distinct and apex only
obscurely truncate, shape in face view ovate to narrowly ovate varying to elliptic,
in profile obscurely inequilateral to subovate (the ventral line often straighter in
optical section than the dorsal line), color in KOH dark chocolate-color immediately, finally becoming slightly paler, in Melzer's dark fulvous, wall about 0.3 p
thick.
Basidia 18-22 x 8-10 u, 4-spored, hyaline in KOH. Brachybasidioles present
in mature hymenium. Pleurocystidia abundant 48-62 x 10-15 pt, fusoid-ventricose,
the neck gradually tapered and apex obtuse, with some mucilaginous material
dried in patches on the neck near the apex, wall thin and hyaline, cell content not
distinctive. Cheilocystidia abundant, either clavate to saccate or fusoid-ventricose
with broadly rounded to obtuse apex, hyaline to dingy yellow in KOH, the former
18-32 x 9-14 pL, the latter 26-38x 10-16 Iu. Caulocystidia rare, a few similar to
the cheilocystidia were found.
Gill trama cocoa-brown to vinaceous-brown in KOH, the walls smooth. Pileus
trama vinaceous in KOH becoming cocoa-color but usually retaining a reddish
tone, hyphal walls smooth. Cuticle of pileus a layer of vesiculose cells several
deep, their walls thin and smooth but weakly brownish to hyaline in KOH. Cortex
hyphae of stipe also weakly flushed vinaceous-gray as revived in KOH as observed
in groups of hyphae. Clamps present.
Type locality. Lower Tahoma Creek, Mt. Rainier National Park, Washington.
Habit and habitat. On debris in mixed forests.
Distribution. Washington.
Observations. This species is one of those ambiguous between Pannucia and
Psathyrella of this work. The shining white stipe, thin white veil, narrow lamellae,
and reaction of hyphae of the stipe in KOH are distinctive.
Subsection Psathyrellae
Series Psathyrellae
Pink tints developing on faded pileus margin and/or the gill edges.
Key to the Species of Series Psathyrellae
1. Spores 14-20 X 6-8,u; lamellae narrow; pleurocystidia 32-44 X 10-16 u.
292. P. megaspora.
1. Not as above. 2
2. Spores not truncate; wall of spore developing a strong violaceous tone in
10-20 minutes in KOH. 293. P. praeatomata.
2. Not as above. 3
3. Scattered fibrils from a thin veil present along the margin of immature pilei. 4
3. Lacking a fibrillose veil of any sort. 6
4. Pleurocystidia rarely over 50 u long; pith of stipe often separating as a thin
rod. 296. P. trepida.
4. Not as above. 5
5. Stipe brown when young; cuticle of pileus mostly of clavate-pedicellate cells.
294. P. fontinalis.
5. Stipe pallid young, darker in age; cuticle of pileus mostly of vesiculose cells.
295. P. opacipes.