The North American species of Psathyrella.

1972]

PSATHYRELLA

409

to clavate or vesiculose and up to 16 / broad, wall smooth, thin and hyaline in all.
Gill trama ochraceous in water mounts of fresh material and deeper ochraceous
revived in KOH. Pileus trama ochraceous to ochraceous-tawny in KOH, the walls
smooth to minutely roughened; cuticle of ellipsoid and vesiculose cells 1-3 deep,
the walls thin, smooth and hyaline to pale brownish in KOH. Clamps present.
Type locality. Science Camp, Medicine Bow National Forest, near Centennial,
Wyoming.
Habit and habitat. Gregarious on soil and humus under aspen.
Distribution. Wyoming.
Observations. The ferruginous pileus and relatively wide spores are a diagnostic combination of characters in this group.
Material examined. Wyoming: Smith 34762, 34853 (Type), 34865.
386. Psathyrella pseudotrepida A. H. Smith, sp. nov.
Pileus 1-3 cm latus, late conicus, glaber rufo-fulvus; lamellae brunneolae
demum brunneo-griseae, latae, subdistantes; stipes 3-5 cm longus, 1-2.5 mm
crassus, hyalinus, deorsum brunneus; velum nullum; sporae 8-9 x 4.5-5 u; pleurocystidia 42-65 x 9-14(-16) /u, fusoide ventricosa, subacuta, cum collis elongatis;
fibulae adsunt. Typus. Smith 73953 (MICH); legit prope Priest Lake, Idaho.
Illust. Text. Figs. 840, 841.
Pileus 1-3 cm broad, obtusely conic with a straight naked margin, expanding
to broadly conic, glabrous, hygrophanous, when fresh dark rusty brown ("Mars
brown" or darker), becoming paler and striatulate on the margin, fading to pale
tan ("cinnamon-buff") on the disc and grayer over marginal area. Context thin
and fragile, odor none.
Lamellae dull brown when young, becoming gray-brown ("hair brown") when
mature, broad, adnate, more or less subdistant, soon seceding, edges even.
Stipe 3-5 cm long, 1-2.5 mm thick at the apex, hyaline-white, naked to the
faintly pruinose apex, becoming dull brown from base upward, veil none.
Spores 8-9x4.5-5 tt, smooth, apical pore well developed, shape in face view
elliptic to ovate, in profile subelliptic to obscurely inequilateral, color in KOH
dark chocolate-color, in Melzer's dark bay, wall about 0.3,u thick.
Basidia 4-spored, 9-11 p/ wide at apex, clavate, hyaline in KOH. Pleurocystidia 42-65x9-14(-16) I,, fusoid-ventricose with long equal neck and obtuse
to subacute apex, walls thin, smooth, hyaline; content not distinctive in either
KOH or Melzer's. Cheilocystidia similar to pleurocystidia but smaller, clavate
to vesiculose cells rare. Caulocystidia not observed except narrowly clavate
hyphal ends scattered here and there.
Cuticle of pileus of inflated (vesiculose) and clavate-pedicellate cells 1-2 deep,
their walls thin and smooth, hyaline to pale cinnamon in KOH; content not distinctive in KOH or Melzer's. Hyphae of trama vinaceous-cinnamon in KOH and
with pigment incrustations (or wall thickenings) on the wall. No distinctive
reaction on any tissue with Melzer's. Clamps present.
Type locality. Tule Bay, Priest Lake, Idaho.
Habit and habitat. Gregarious on soil, October.
Distribution. Idaho.
Observations. The spores are much too small for P. trepida but otherwise the
two are quite similar.
Material examined. Idaho: Smith 58754, 70163, 73953 (Type), 73954.