The North American species of Psathyrella.

1972]

PSATHYRELLA

219

Pileus cuticle a layer of vesiculose cells 2-3 deep, the uppermost with hyaline
walls, those toward the subcutis with ochraceous walls. Hyphae of subcuticular
region vinaceous-cinnamon in KOH when first revived, fading to pale cinnamon,
walls smooth or nearly so. Clamp connections present.
Type locality. Europe.
Habit and habitat. Cespitose-gregarious on wet earth.
Distribution. California, Idaho, Michigan, Washington.
Observations. Some pleurocystidia are narrowly utriform but the typical range
is from an obtuse to a subacute apex. Some of the cystidia showed a refractive
wall but most did not. Nathorst-Windahl (1961) described and discussed his
collections from Sweden. My concept of the species appears to correspond well
with his. The species is rare in my collecting areas also.
Material examined. California: Smith 56922. Idaho: Smith 44783, 58627,
70173, 73914. Michigan: Smith 78202. Washington: Smith 48102, 49361, 49363.
176. Psathyrella bifrons (Berkeley) A. H. Smith, Contr. Univ. Mich. Herb. 5:
40. 1941.
Agaricus bifrons Berkeley, Smith English Flora 5: 114. 1836.
Psathyra bifrons (Berk.) Quelet, Champ. Jura et Vosges, Suppl. 7: 52. 1880.
Drosophila bifrons (Berk.) Quelet, Enchir. Fung. 117. 1886.
Illust. Text Figs. 398, 399.
Pileus 1-2 cm broad, obtusely conic, remaining so or the margin flaring slightly,
sometimes campanulate, surface at first densely white-fibrillose from the remnants
of the outer veil, the fibrils becoming arranged into recurved evanescent scales,
margin appendiculate, entirely glabrous in age, color beneath the scales pale buff
and gradually changing to sordid cinnamon-brown, hygrophanous, fading to
sordid tan. Context very thin and fragile, pallid to watery brown, odor and taste
not distinctive.
Lamellae crowded, moderately broad, adnate, equal, white when young, soon
tinged brownish and in age "cinnamon-brown," finally with a smoky tinge,
margin even.
Stipe 6-10 cm long, 3-5 mm thick, tubular, very brittle, watery white, covered
by loose white fascicles of fibrils up to the densely pruinose apex, glabrescent, the
base at times slightly enlarged.
Spores 8-11 x 4.5-5.5 [, smooth, apical pore prominent and apex broadly truncate, shape in face view elliptic (pointed at the base in many) to subovate, in
profile somewhat inequilateral to obscurely so, color in KOH near bister slowly
changing to chocolate-brown, in Melzer's reddish tawny, wall about 0.6 U thick.
Basidia 4-spored, 18-24x7-11 A, hyaline in KOH. Brachybasidioles present
in old specimens (the basidioles inflate considerably). Pleurocystidia absent or
a few near the edge and similar to cheilocystidia. Cheilocystidia numerous, 40 -62x8-12(-15) [/, fusoid-ventricose with apex subacute, some saccate to clavate
and 9-14, wide, wall thin, smooth and usually hyaline.
Gill trama regular, the hyphae somewhat interwoven and with the cells inflated,
hyaline or nearly so in KOH. Pileus having a cuticle of hyaline vesiculose cells
several deep, walls thin, smooth and hyaline, content not distinctive in KOH or
in Melzer's. Hyphae of the trama of enlarged hyaline cells with smooth walls.
Clamp connections present. No distinctive reactions noted for any tissue revived
in Melzer's.
Type locality. British Isles.