The North American species of Psathyrella.

1972]

PSATHYRELLA

167

only slightly striatulate when moist, veil remnants white. Context moderately
thick and fragile, brownish fading to buff, odor and taste not distinctive.
Lamellae broad (5-8 mm), adnate, seceding, close, grayish tawny in buttons,
becoming somewhat reddish and finally nearly black but dull rusty red when
dried, edges white-fimbriate.
Stipe 4-6 cm long, 4-7 mm thick at apex, hollow, equal or slightly enlarged
downward, white and unchanging, densely white-fibrillose to fibrillose-squamulose
up to the zone left by the broken veil, striate and pruinose above, in age slightly
enlarged.
Spores 7-9(-10) x 4-4.5 p (some 8-10x2.5-3 t), smooth, with an apical pore
which is indistinct (the apex not truncate), shape in face view ovate to narrowly
ovate, more rarely suboblong, in profile somewhat to obscurely inequilateral, color
in KOH dingy ochraceous-tawny to somewhat cocoa-color, in Melzer's tawny to
reddish tawny, wall about 0.3, thick.
Basidia 2- and 4-spored, 17-24x8-10 /, clavate, hyaline in KOH. Pleurocystidia abundant, 46-60 x 9-16 u, thin-walled, hyaline in KOH, fusoid-ventricose
with obtuse (mostly) to subacute (rarely) apex, when first revived in KOH with
bits of debris or mucilaginous material on the neck or near or over the apex, wall
thin and colorless, cell content not distinctive in either KOH or Melzer's. Cheilocystidia similar to pleurocystidia but varying to subcapitate, clavate and
vesiculose, 30-40x 12-18 t. Caulocystidia not found.
Gill trama sordid brown to nearly hyaline in KOH, with scarcely a tinge of
vinaceous, hyphal cells greatly inflated at maturity. Pileus with a cuticle of a
layer of vesiculose hyaline cells about 2 deep, walls thin and smooth, content not
distinctive. Hyphae of the trama dingy brownish fading to nearly hyaline, the
walls smooth in KOH. Clamp connections present. No distinctive reactions
observed in mounts made in Melzer's.
Type locality. Fowlerville, Michigan.
Habit and habitat. On rotting elm and ash logs, October.
Distribution. Known only from the type locality.
Observations. The spores, after two hours in KOH, are clouded gray but are
still pale in color. The broad gills, copious veil remnants on the stipe, pale (almost
ochraceous-tawny) spores when first mounted in KOH, obtuse cystidia and the
relatively pale color of the tramal hyphae in KOH (when one considers the color
of the moist pileus) are distinctive.
Psathyrella iterata var. ochraceispora may represent a distinct species but
more collections are needed to verify this. The color of the spores as revived in
KOH distinguishes it from var. iterata and from P. paradoxa. P. paradoxa var.
velicopia is distinct from both var. paradoxa and P. iterata var. iterata in narrow
spores (3-3.5 p wide as compared to 3.5-4.5 /u wide) and var. velicopia also has
a more membranous inner veil which at times forms a baggy annulus on the stipe.
Also, it was not observed to have cystidia colored even slightly by KOH.
Psathyrella paradoxa var. paradoxa and P. iterata var. iterata are very close but
P. paradoxa var. paradoxa has cystidia some of which are grayish vinaceous in
KOH and the stipe becomes brown at the base. In P. iterata the cystidia remain
hyaline and the stipe white.
The above four variants are discussed as a group here because I consider it
likely that a critical biological study of the group will be needed to clarify species
concepts. At present I prefer to treat them as presented here in order not to
obscure any diversity in characters found to be taxonomically valuable in other