The North American species of Psathyrella.

1972]

PSATHYRELLA

317

Habit and habitat. Gregarious on black muck in a spring area.
Distribution. Known only from the type locality.
Observations. The dark medium-sized spores, branched pleurocystidia, occasional gigantic vesiculose cheilocystidia, habitat, dark brown pileus and thin veil
are distinctive. Branched pleurocystidia are seen in many species of Psathyrella,
especially in species with utriform pleurocystidia, but in the present species by far
the majority of basidiocarps show this feature.
287. Psathyrella pseudofulvescens A. H. Smith, sp. nov.
Pileus 6-12(-15) mm latus, convexus vel subplanus, glaber pallide fulvus;
lamellae confertae, angustae, pallidae demum brunneo-griseae; stipes 2-3 cm
longus, circa 1 mm crassus, glaber, deorsum melleibrunneus; sporae 9-12 x 5-6 t;
pleurocystidia 46-62x9-16 ~/, fusoide ventricosa, acuta; fibulae adsunt. Typus.
Smith 30174 (MICH); legit prope Tahoma Creek, Mt. Rainier National Park,
Washington.
Illust. Text Figs. 618-621.
Pileus 6-12(-15) mm broad, obtusely conic expanding to convex or nearly
plane, surface glabrous except for inconspicuous marginal fibrils, moist and
hygrophanous, pale ochraceous-tawny fading to pale buff, translucent striate
moist. Context very thin and fragile, odor and taste not recorded.
Lamellae close, narrow, ascending-adnate, pallid when young, near "hair
brown" at maturity, drying with a cinnamon tinge, edges not becoming pink in
faded pilei.
Stipe 2-3 cm long, 1 mm thick or less, equal, fragile, glabrous or at first only
with scattered fibrils lower down, whitish at first, at maturity honey color over
lower portion.
Spores 9-12 x 5-6 u, smooth, apical pore distinct but not prominent, spore apex
with a slight truncation, shape in face view broadly ovate to elliptic, in profile
subovate to obscurely inequilateral varying to elliptic, color in KOH bister becoming paler and avellaneous with an ochraceous tinge, finally the darkest ones
chocolate-color (many remaining pallid in KOH mounts), in Melzer's ochraceoustawny, wall about 0.3 ) thick.
Basidia 4-spored, 17-24 x9-11 I, broadly clavate, hyaline in KOH. Brachybasidioles present at maturity. Pleurocystidia scattered, 46-62 x 9-16 ju, fusoidventricose with a flexuous narrow neck ending in an acute to subacute apex,
hyaline, thin-walled, smooth, content not distinctive. Cheilocystidia similar to
but often smaller than the pleurocystidia but some saccate cells also present,
hyaline in KOH. Caulocystidia ventricose at base with a long tapering to an equal
flexuous neck, 50-80 x 8-12 x 3-5 p, hyaline in KOH, wall smooth and thin.
Hyphae of stipe cortex hyaline except near the septa where fulvous pigment
deposits occur (as revived in KOH), the septa also fulvous in KOH in many
instances.
Gill trama dingy brownish becoming hyaline in KOH. Pileus trama sordid
tawny becoming hyaline, the walls with only inconspicuous pigment deposits;
cuticle of pileus a layer of vesiculose cells more or less 1-2 cells deep, the cells
hyaline or nearly so in KOH. Clamp connections present.
Type locality. Lower Tahoma Creek, Mt. Rainier National Park, Washington.
Habit and habitat. On debris under alder, vine-maple, etc.
Distribution. Washington.
Observations. This is one of the few species known to me at present in which