The North American species of Psathyrella.

1972]

PSATHYRELLA

187

Lamellae moderately close, 18-20 reach the stipe, broad, adnate, whitish but
soon cocoa-brown, dark reddish brown in age, edges even.
Stipe 1-2 cm long, about 1 mm thick, equal, fragile, densely white-fibrillose
from the veil remnants, apex pruinose or with minute fibrillose flecks.
Spores 8-11 x 5-6 1u, smooth, truncate because of a broad apical pore, shape in
face view broadly elliptic to broadly ovate, in profile view obscurely inequilateral,
color in KOH bister becoming chocolate-brown, finally fuscous, in Melzer's
"tawny," wall about 0.4 ) thick.
Basidia 4-spored, 17-24x 8-10(-12) p%, clavate, hyaline in KOH, when sporulating projecting slightly. Basidioles more or less inflated by late maturity and
brachybasidiole-like. Pleurocystidia absent but rarely one finds large cylindric
cells (28-35 x 10-15 [) projecting into the hymenium from the inner subhymenium
or the gill trama proper. Cheilocystidia 28-43 x 9-14 a, fusoid-ventricose to
clavate, wall thin, smooth and hyaline (or rarely a few granules adhering along
the neck), cell content not distinctive.
Gill trama of greatly enlarged irregularly arranged cells, hyaline or only dull
brownish (in groups) in KOH. Pileus trama of loosely arranged greatly enlarged
hyphal cells dull brownish in KOH fading to nearly hyaline, lacking any appreciable incrustations. Cuticle of inflated cells 30-50 / wide, globose to clavate and
arranged in an irregular manner, wall thin, smooth and hyaline to yellowish in
KOH, cell content not distinctive. Clamp connections present.
Type locality. Near Milford, Michigan.
Habit and habitat. Scattered on debris at edge of swamp.
Distribution. Known only from the type locality.
Observations. No caulocystidia were observed on the one stipe studied. The
white pileus at first and wide spores are distinctive.
Subsection Mixtae A. H. Smith, subsect. nov.
Sporae (8-) 9-12x5-7 M vel maior; pleurocystidiis utriformibus vel late
rotundatis. Typus. Psathyrella brooksii.
Key to the Species of Subsection Mixtae
1. Lamellae blue when young; spores 12-13 X 6.5-7.5,. 148. P. saponacea.
1. Not as above. 2
2. Spores 12-15 X 7-9 A; pleurocystidia subclavate, elliptic, or broadly fusoidventricose. 149. P. brooksii.
2. Spores smaller. 3
3. Hyphae of stipe with pigment-deposits near the septa; clamps rare; pileus flushed
pale salmon along the margin after fading. 150. P. salmonescens.
3. Not as above. 4
4. Brachybasidioles present at maturity; pileus margin uplifted and splitting in
age; context crumbly-fragile. 151. P. fatiscens.
4. Not with above combination of features. 5
5. Spore apex at most obscurely truncate; pleurocystidia in optical section mostly
pedicellate-elliptic to subelliptic. 152. P. vulgaris.
5. Not as above (spore apex distinctly truncate). 6
6. Pileus cuticle a palisade of clavate to vesiculose cells. 145. P. riparia.
6. Pileus cuticle about 2 cells deep. 7
7. Cespitose, arising from a basal mat of mycelium and stipes often connate.
146. P. emmetensis.
7. Cespitose-gregarious along roads. 147. P. vialis.