The North American species of Psathyrella.

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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

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Distribution. Michigan, Washington, Wyoming.
Observations. The pale color when young, gray gills at maturity and lack of
pink tints in age are distinctive.
Material examined. Michigan: Smith 33616. Washington: Imshaug 800;
Smith 29348 (Type), 29358, 30224. Wyoming: Smith 35262.
318. Psathyrella coloradensis A. H. Smith, sp. nov.
Pileus 6-15 mm latus, convexus, ad marginem leviter fibrillosus, glabrescens,
fusco-cinnamomeus; lamellae latae, subdistantes brunneolae demum fuscobrunneae; stipes 2-4 cm longus, 1-2 mm crassus, albus, deorsum demum brunneus, glabrescens; velum sparsissimum; sporae 13-15.5 x 6-7.5 /; pleurocystidia
40-60 x 10-15 A, fusoide ventricosa, acuta; fibulae adsunt. Typus. Smith 51659
(MICH); legit prope Placerville, Colorado.
Pileus 6-15 mm broad, convex with an appressed margin at first, expanding
to broadly convex or retaining a slight obtuse umbo. A thin fibrillose veil leaving
scattered fibrils along the margin at first but pileus soon completely glabrous.
Pileus moist and hygrophanous, dark cinnamon-brown, when faded a dingy tan
and distinctly atomate, when old dark chocolate-brown except for a pallid disc.
Context thin and fragile, odor not distinctive, taste mild.
Lamellae broad, subdistant, broadly adnate, dull brown becoming dark
chocolate-brown, edges pallid.
Stipe 2-4 cm long, 1-2 mm thick, equal, fragile, whitish above, brownish below,
lower portion fibrillose from remains of a thin veil but glabrescent.
Spores blackish in deposit, 13-15.5 x 6-7.5 a, smooth, apex truncate from an
apical pore, shape in face view elliptic to subovate, in profile obscurely inequilateral to subelliptic, color in KOH blackish brown when mature, in Melzer's
dark reddish tawny, wall about 0.6 p thick.
Basidia 4-spored, 26-30x 9-12 a, clavate, hyaline. Brachybasidioles possibly
present at maturity. Pleurocystidia scattered 40-60x 10-15,a, fusoid-ventricose
(pedicel 10-15 x 3 u, neck 15-20 x 3-3.5 a, apex pointed), hyaline, smooth, thinwalled, cell content not distinctive. Cheilocystidia similar to but smaller than
pleurocystidia and lacking a narrow pedicel, apex acute; clavate to vesiculose
cells with yellow walls in KOH also present, 8-14 JL wide.
Pileus cuticle about 2 cells deep, the cells greatly inflated, thin-walled and
hyaline to ochraceous in KOH. Subcuticular hyphae dingy brown in KOH but
fading, with incrusted pigment. Clamp connections present.
Type locality. Placerville, Colorado.
Habit and habitat. Gregarious on debris under willows and brush near a
stream, August.
Distribution. Colorado.
Observations. The pilei were not plicate striate and it is questionable if the
inflated basidioles can be properly described as brachybasidioles, but it is obvious
to me that one could interpret them either way without changing the taxonomic
import of the character state in the genus.
Section Fatuae (Romagnesi) Singer, Sydowia 15: 67. 1961
Drosophila sect. Fatuae Romagnesi, Bull. Soc. Linn. Lyon 13: 51. 1944.
Type. Psathyrella fatua.