The North American species of Psathyrella.

1972] PSATHYRELLA 213
Habit and habitat. On debris under aspen and sumac on very wet soil in the
marginal ditch of a bog, scattered to gregarious, June.
Distribution. Michigan, North Carolina, Ohio.
Observations. The yellow pileus when young, pale buff veil, and the large
pleurocystidia are distinctive. The type of variation in spore size and shape
encountered here is known for many groups of fleshy fungi even including the
genus Rhizopogon, and probably indicates irregularity in the meiotic divisions.
Material examined. Michigan: Kauffman 6-27-20; Potter 5004; Smith 5
(Type), 20409, 25214, 25215, 26242. North Carolina: Hesler 16380. Ohio:
Walters 160.
170. Psathyrella tenuivelata A. H. Smith, sp. nov.
Pileus 2-3 cm latus, convexus demum late convexus, sparsissime fibrillosus,
glabrescens, fumoso-cinnamomeus; lamellae confertae latae (~+5 mm), avellaneae
demum triste vinaceo-brunneae; stipes 2-3 cm longus, 2-4 mm crassus, deorsum
avellaneus, fibrillosus, glabrescens; velum pallide melleum; sporae 7-9(-10)x
5-6.5 (-7) u, pleurocystidia (36-) 42-64 x 9-13 /, pedicellato-elliptica vel fusoide
ventricosa, ad apicerum obtuse vel rotundata; fibulae adsunt. Typus. Smith 15020
(MICH); legit prope Milford, Michigan.
Illust. P1. 60, fig. a; Text Figs. 382-385.
Pileus 2-3 cm broad, convex, the margin appressed against the stipe when
young, expanding to broadly convex, at first more or less covered with thin
appressed patches of pale buff fibrils, the margin at first with a faint fibrillose
fringe, opaque but becoming faintly translucent striate before fading, when moist
"warm sepia" (dark dingy cinnamon), fading to dark avellaneous ("wood
brown"). Context thin and very fragile, pale brownish, odor and taste mild.
Lamellae horizontally adnate, close, 23-35 reach the stipe, 3 tiers of lamellulae, broad (about 5 mm), oval in outline, pale avellaneous becoming dull dark
vinaceous-brown ("bone brown") to "Natal brown," edges eroded.
Stipe 2-3 cm long, 2-4 mm thick, equal or slightly enlarged below, hollow
fragile, pallid above, dull avellaneous toward the base, lower two-thirds covered
by a thin coating of buff fibrillose remains of the veil, glabrous in age.
Spores 7-9(-10) x 5-6.5(-7) /u, smooth, a broad lens-shaped pore present but
apex at most only obscurely truncate, shape in face view broadly elliptic to
obscurely angular-elliptic, in profile broadly subelliptic to broadly and obscurely
inequilateral to slightly bean-shaped, wall about 0.4 A thick, color in KOH soon
chocolate-brown revived in KOH, in Melzer's pale to rich tawny to reddish tawny.
Basidia 4-spored, 18-24x 7.5-11 /u, clavate, hyaline in KOH. Pleurocystidia
scattered, (36-)42-64 x9-13 /A, pedicellate-elliptic to fusoid-ventricose, the apex
broadly rounded but in many with one or more finger-like protuberances, wall
thin, smooth and hyaline, content of cell not distinctive in KOH or Melzer's.
Cheilocystidia mostly clavate, saccate or more or less ellipsoid, 22-36(-60) x
9-15 /u, thin-walled and hyaline in KOH, a few ventricose cells also present and
some of these bearing finger-like processes near or at the apex, wall smooth,
hyaline, thin, cell content not distinctive. Caulocystidia scattered, subfusoid and
100-200 x 10-20 It, hyaline, wall thickened to 0.5,, cell content in some appearing
"colloidal" (opalescent).
Gill trama of parallel to loosely interwoven hyphae pale vinaceous-brown
becoming nearly hyaline (as revived in KOH), water mounts of fresh material
pale brownish. Pileus trama dull cocoa-brown in KOH, the pigment incrusted