The North American species of Psathyrella.

1972]

PSATHYRELLA

393

truncation, shape in face view elliptic to obscurely ovate, in profile elliptic to
obscurely inequilateral, color in KOH dark chocolate-color as soon as mounted,
paler and more of a chocolate-brown on standing, finally violaceous-fuscous,
reddish tawny in Melzer's, wall about 0.4 Au thick.
Basidia 4-spored, 8-9 M broad, short-clavate, hyaline in KOH. Pleurocystidia
scattered, 36-48x 10-15 g, fusoid-ventricose, apex subacute to acute, apical area
on some finely granular, wall thin and hyaline, cell content not distinctive.
Cheilocystidia similar to pleurocystidia or smaller; clavate cells also present.
Pileus cuticle of inflated cells pale cinnamon in KOH, wall thin and smooth,
the layer 2-3 cells deep. Hyphae of subcuticular area vinaceous-cinnamon in
KOH, with pigment thickenings near the septa. Clamps present.
Type locality. Priest River Experimental Forest, Priest River, Bonner County,
Idaho.
Habit and habitat. Gregarious on soil with lignicolous debris in it, September.
Distribution. Idaho, Michigan.
Observations. The darkly colored pileus, lack of a veil, fairly small spores
(which become violaceous-fuscous on standing in KOH), and acute pleurocystidia
are distinctive.
Material examined. Idaho: Smith 73547, 73951 (Type), 73952. Michigan:
Smith 67056.
369. Psathyrella lactobrunnescens A. H. Smith, sp. nov.
Pileus 10-15 mm latus, conicus, glaber, albidus, demum griseo-brunneus;
lamellae latae confertae, albidae demum fusco-griseae; stipes circa 2 cm longus,
1.5 mm crassus, albidus, glaber; sporae 7-8.5 x 4-4.5 x 4.5-5 u; pleurocystidia
34-46x9-13 g, subutriformia vel subfusoidea, obtusa; fibulae adsunt. Typus.
Smith 57709 (MICH); legit prope White House Landing, Tahquamenon River,
Chippewa County, Michigan.
Illust. Text Figs. 773-775.
Pileus 10-15 mm broad, obtusely conic and hardly expanding, surface glabrous,
moist, hygrophanous, white and translucent-striate when young, gradually becoming grayish brown as spores mature but when faded white again. Context very
thin and delicate, odor none, taste not recorded.
Lamellae close, broad, adnate, soon seceding, white becoming drab from the
spores, edges even.
Stipe about 2 cm long, 1.5 mm thick at apex, equal or slightly enlarged downward, white and unchanging or merely watery in age, apex scarcely pruinose,
naked and undulating downward.
Spores 7-8.5 x 4-4.5 x 4.5-5 ), smooth, apical pore distinct, shape in face view
broadly ovate to elliptic, in profile obscurely bean-shaped to obscurely inequilateral, color in KOH at first dark cocoa-brown, slowly becoming darker, reddish
tawny in Melzer's, wall about 0.2 u thick.
Basidia 4-spored, 8-9 u wide. Pleurocystidia abundant, 34-46 x 9-13 gL, subfusoid to subutriform, neck not well-differentiated, apex obtuse or rarely rounded,
walls thin and hyaline, content not distinctive in either KOH or Melzer's. Cheilocystidia 13-30 x 12-18 /, vesiculose to subclavate or 25-37 x 10-15 g and broadly
fusoid, vesiculose cells at times with a pale smoky brown content as revived in
KOH, walls smooth, hyaline or weakly ochraceous (rarely) as revived in KOH,
some cells similar to the pleurocystidia. Caulocystidia scattered and clavate to
elliptic, 40-67x 15-25 p, thin-walled, smooth and hyaline, near apex of stipe
versiform and more like the cheilocystidia.