The North American species of Psathyrella.

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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

[VOL. 24

wood brown (grayish brown), close, narrow becoming moderately broad, tapered
to the edge of the pileus; edges even and pallid.
Stipe 4-11 cm long, 2-3.5 mm thick, equal, very fragile and weak, hollow,
faintly silky at first, in age naked, pallid to dingy pallid overall, in age slightly
more so but no distinct color change in the lower part, weakly strigose over the
basal area.
Spore deposit violaceous-brown. Spores 11-14x5.5-7 a, smooth, apical pore
present but apex not truly truncate, shape in face view suboblong to elliptic or
slightly ovate, in profile slightly bean-shaped to subelliptic (ventral line flattened
slightly); color in KOH chocolate-color (medium), in Melzer's rusty tan and
apical pore more distinct than in KOH, wall about 0.3 t thick.
Basidia 4-spored, short-clavate, 9-13 t wide. Brachybasidioles present at late
maturity. Pleurocystidia nine-pin-shaped to fusoid-ventricose with an obtuse
apex, 36-57x10-17 iL, thin-walled, smooth, hyaline in KOH. Cheilocystidia
30-56 x 8-14 A, fusoid-ventricose with obtuse apex, hyaline in KOH, thin-walled.
Caulocystidia 30-60 x 9-17 t, rare, roughly resembling the pleurocystidia but the
apical inflation often larger, some with amorphous content in KOH.
Gill trama of much inflated nearly hyaline-walled cells. Pileus trama weakly
ochraceous, the hyphae smooth or some debris on the wall (but no typical
incrustations present). Cuticle a palisade of clavate to inflated-pedicellate cells
14-30 [t wide, walls hyaline to merely ochraceous in KOH. Clamps present.
Type locality. Near Adrian, Michigan.
Habit and habitat. Gregarious under Impatiens (jewel weed), May.
Distribution. Known only from the type locality.
Observations. The species is likely to be confused in the field with P. conopilea
but it lacks setae on the pileus, has smaller spores and pleurocystidia are present.
Drosophila polycystis Romagnesi appears to be close to this species.
299. Psathyrella atomata (Fries) Quelet, Champ. Jura et Vosges 153. 1872.
Agaricus atomatus Fries, Syst. Mycol. 1: 298. 1821.
Psathyra atomata (Fr.) Kummer, Fiihr. Pilzk. 70. 1871.
Drosophila atomata (Fr.) Kiihner & Romagnesi, Fl. Anal. 355. 1953.
Pileus 10-25 mm broad, obtusely conic to campanulate, hygrophanous, when
moist grayish with a tinge of ocher on the disc, fading to whitish or becoming pale
pink ("hydrangea pink") after fading, atomate, striate when moist, even or
wrinkled when faded. Context membranous and fragile, odor and taste not
distinctive.
Lamellae adnate, subdistant, 12-16 reach the stipe, broad and becoming ventricose, whitish, becoming black from the spores, edges often pinkish in age.
Stipe 3-5 cm long, 1-2 mm thick, equal, very fragile and often lax, tubular,
white, pulverulent over upper portion but soon glabrescent.
Spores 11-13 (-15) x 6-7 (-8) A, smooth, apical pore distinct and apex truncate
(under oil-immersion), shape in face view suboblong to elliptic, in profile subelliptic, color in KOH coffee-bean color when first revived, darkening slowly, in
Melzer's dull reddish brown, wall about 1,u thick.
Basidia 18-26 x 9-12 u, 4-spored, clavate, hyaline in KOH. Brachybasidioles
present on mature hymenium. Pleurocystidia absent to rare or scattered and similar to cheilocystidia. Cheilocystidia 35-48 x 9-14 /, fusoid-ventricose, apex acute
to subacute, neck at times greatly elongated (up to 40 / long) and 3-4 JL thick,
wall thin, smooth and hyaline, cell content not distinctive in KOH.