The North American species of Psathyrella.

1972]

PSATHYRELLA

137

cinnamon as revived in KOH but fading to ochraceous on standing. Clamps
present. No amyloid reaction noted on any tissue.
Type locality. White House Landing, Tahquamenon River, Chippewa County,
Michigan.
Habit and habitat. Cespitose on hardwood logs, September.
Distribution. Known only from type locality.
Observations. The distinguishing features of this species are the numerous
vesiculose cheilocystidia, the denticulate veil remnants on the pileus margin, the
darkening stipe beneath the veil fibrils, and relatively narrow spores-at least
narrower than in P. velibrunnescens to which it is rather similar in some respects.
91. Psathyrella candidissima A. H. Smith, Mycologia 42: 122. 1950.
Illust. I. c. figs. 16g, h; 18, a.
Pileus 2-4 cm broad, obtusely conic at first, expanding to plane with a low
obtuse umbo, surface at first coated with the layer of snow-white fibrils more
or less radially arranged and which become aggregated into fascicles before
disappearing entirely, surface glabrous in age, snow-white when young, (beneath
the fibrils) and the margin appendiculate from veil fragments, scarcely changing
color in age (the disc creamy in oldest pileus), the edge finally naked. Context
brittle but also soft, watery-pallid fading to white, odor and taste not distinctive,
no color change on bruising.
Lamellae close, thin, narrow, ascending-adnate and soon seceding, snow-white
becoming "light drab," edges even.
Stipe 5-10 cm long, 4-6 mm thick at apex, equal, hollow, fibrous, snow-white
throughout, surface floccose-fibrillose from the veil and at first with a slight
evanescent zone near the apex or above the middle, floccose-pruinose above this.
Spores 8-10.5 x4-5 a, smooth, truncate from a distinct apical pore, in face
view ovate to elliptic, in profile subelliptic to obscurely inequilateral, color in
KOH dark chocolate or chocolate-gray on less mature spores, in Melzer's baybrown to slightly redder, wall about 0.4 g thick.
Basidia 4-spored, clavate, hyaline in KOH, 18-26 x 7-9 /. Pleurocystidia
scattered to abundant, ventricose with a short neck and broadly rounded apex
or varying to utriform or to pedicellate-subelliptic (in optical section), smooth,
with a very slightly thickened and more highly refractive wall over the sides
than at the apex, hyaline in KOH, content not distinctive. Cheilocystidia abundant 32-50 (-68) x 10-15 g, elongate-subfusoid with obtuse apex to utriform or
broadly fusoid-ventricose, thin-walled, hyaline in KOH, some small inflated to
clavate cells also present. Caulocystidia in fascicles, resembling the cheilocystidia
but usually some with walls 0.5 K thick and highly refractive.
Pileus with a cuticle of vesiculose cells somewhat larger than the hyphae of
the context and hyaline in KOH, 2-3 cells deep, content not distinctive. Tramal
hyphae of pileus and lamellae perfectly hyaline in KOH and lacking any
distinctive reactions in Melzer's. Clamp connections not present.
Type locality. Lower Tahoma Creek, Mt. Rainier National Park, Washington.
Habit and habitat. Gregarious on debris under alder.
Distribution. Michigan and Washington.
Observations. The white pilei, medium-sized spores, tendency for the caulocystidia to have slightly thickened highly refractive walls, and lack of clamp
connections are diagnostic.
Material examined. Michigan: Smith, 74614. Washington: Smith 29871
(Type).