The North American species of Psathyrella.

1972]

PSATHYRELLA

147

Illust. Smith, 1. c. pls. 14; 15; 26, figs. 1, 2, 9. P1. 49; P1. 53, fig. b; Text Figs. 250 -252.
Pileus (1-)2-5 cm broad, obtusely conic, expanding to broadly conic, margin
straight at first, glabrous except for the weakly appendiculate margin, the veil
thin and submembranous to fibrillose, color dingy honey brown or slightly
darker than "buckthorn brown" to (rarely) dull cinnamon, hygrophanous, fading
to pale pinkish buff (pallid tan to dingy pallid) but disc later darkening to pale
tan. Context thin and fragile, brownish fading to pallid, odor and taste not
distinctive.
Lamellae close, broad, adnate, seceding, pallid brownish becoming cinnamondrab, edges whitish, gills blackish as dried.
Stipe (3-)4-11 cm long, 3-5 mm thick at apex, equal, fragile, whitish over
all at first, becoming dingy over the upper part but base remaining pallid,
sparsely fibrillose over lower half, downy-pruinose above; all traces of the veil
soon vanishing from the stipe.
Spores 8-10x4.5-5.5(-6) a, smooth, apical pore distinct, shape in face view
elliptic to ovate, in profile subovate to obscurely inequilateral, color in KOH
soon dark chocolate-color, in Melzer's bay-red, wall about 0.4 j thick.
Basidia 4-spored, clavate, 17-23 x 7-9 p. Pleurocystidia scattered, 36-48 X
9-14 u, utriform to narrowly utriform, the apex typically subcapitate, thin-walled,
smooth, hyaline in KOH or Melzer's, the content not distinctive. Cheilocystidia
mostly clavate to saccate, 30-38 x 9-15 a, hyaline in KOH, some fusoid-ventricose
and 28-40 x 10-13 A, the apex merely obtuse, content not distinctive. Caulocystidia clavate to fusoid-ventricose with obtuse apex, the latter 34-46 x 9-15 ~,
apex obtuse, thin-walled and hyaline, not abundant.
Cuticle of pileus a staggered palisade of clavate to vesiculose cells, the walls
hyaline to yellowish in KOH and smooth. Subcuticular region faintly dull
cinnamon in sections (in KOH) but fading, cells smooth, trama soon hyaline in
KOH. Clamps present. No distinctive reactions on any tissue in mounts made
in Melzer's.
Type locality. Pasadena, California.
Habit and habitat. Gregarious on humus under brush and hardwood trees,
especially cottonwood, summer and fall.
Distribution. California, Colorado, Idaho, Michigan, New Mexico, Oregon,
Utah, Washington, Wyoming.
Observations. This very "ordinary" appearing Psathyrella appears to be
closely related to the European species P. fusca. For a comparison see that
species. Its diagnostic features are the spores mostly over 5 p wide, utriform
pleurocystidia, appendiculate pilear margin, lack of fibrillose squamules over
the pileus at any stage, and the weak pigmentation in KOH of the hyphae of
the subcuticular region of the pileus.
Material examined. California: Pusateri 36, 131; Colorado: Smith 51771,
51772, 51774, 51775, 51777, 51778, 51779, 51780, 51781, 51782. Idaho: Smith
47183, 47185, 47188, 47280, 65856, 73945, 73948, 73949, 73950(?). Michigan.
Ammirati 3527; Smith 25498. New Mexico: Barrows 1877. Oregon: Smith 19414,
19420, 19451, 19565, 19704, 23816, 23827, 23874, 24732, 27796. Utah: McKnight
F988, F989. Washington: Cooke 19820, 21725, 22623; Smith 3317, 13852, 14161,
14165, 14177, 14249, 14259, 14271, 14281, 14533, 14565, 14566, 14588, 14730, 16891,
29513, 29520, 29521, 30216. Wyoming: Smith 34506, 34544, 34614, 34789, 34879.