The North American species of Psathyrella.

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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

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Bigelow 3790. Michigan: Ammirati 2711, 2728, 2811; Kauffman 9-19-06; Potter
4492, 4767, 4912, 6810, 7181; Smith 33-966, 21466, 21906, 23408, 25497, 33448,
33500, 43327, 43329. Oregon: Gruber 16-8; Smith 9292, 55588. Tennessee:
Smith 10767. CANADA. Nova Scotia: Harrison 8023.
360. Psathyrella betulina Peck, Bull. Torrey Club 34: 101. 1907.
Illust. Text Figs. 805, 806.
Pileus 1.2-2.5 cm broad, conic or convex, sometimes broadly umbonate, surface
glabrous, atomate, hygrophanous, fuscous to dark brown when moist, paler when
dry. Context thin, membranous or submembranous, fragile.
Lamellae subdistant, cinereous becoming black, white on the margin, broadly
adnate, broad when mature.
Stipe 2-4.5 cm long, 1-2 mm thick, fragile, equal, hollow, glabrous, shining
white.
Spores 8-10x 4.5-5.5,/, smooth, apical pore present and apex truncate under
an oil-immersion lens, shape in face view elliptic to slightly ovate, in profile
slightly ovate to more or less elliptic or obscurely inequilateral, color in KOH
date brown becoming dark chocolate-color, in Melzer's bay-red, wall about 0.6 u
thick.
Basidia 4-spored, 14-18 x6-8 I,, clavate, hyaline in KOH. Pleurocystidia
scattered, 40-54(-60)x 10-15 /t, fusoid-ventricose, the apex obtuse to subacute,
wall thin and hyaline, smooth, cell content not distinctive. Cheilocystidia 26-38 x
8-12 /A, subclavate to subfusoid or fusoid-ventricose but with a very short neck,
hyaline in KOH, smooth.
Pileus having a cuticle of vesiculose hyaline cells with some pedicellate cells
intermingled but not in a true palisade, occasional fusoid-ventricose pileocystidia
projecting from the cuticle. Context of interwoven hyphae, pale tan to pallid
when revived in KOH. Clamp connections present.
Type locality. Stow, Massachusetts.
Habit and habitat. On decaying branches of white birch.
Distribution. Massachusetts, Michigan, North Carolina.
Observations. The grayish lamellae which become black, the shining white
stipe, relatively wide dark colored (in KOH) spores, and relatively uncolored
(in KOH) hyphae of the subcuticular region of the pileus are distinctive.
Material examined. Massachusetts: Peck's Type. Michigan: Smith 33-1093,
20961, 20974, 21023, 23401, 25452, 25533, 25621, 33498, 34006, 35994. North
Carolina: Hesler 14693.
361. Psathyrella subargillacea A. H. Smith, sp. nov.
Pileus 2-3 cm latus, late conicus, glaber, pallide argillaceus; contextu pallide
argillaceus; lamellae latae distantes vel subdistantes, brunneolae demum sordide
vinaceo-brunneae; stipes 2.5-3 cm longus, 1-1.5 mm crassus, albidus, sericeofibrillosus; velum sparsum; sporae 8-11 x 4-5 (-6) /; pleurocystidia 52-68 (-75) x
10-16, late fusoideo-ventricosa, obtusa; fibulae adsunt. Typus. Smith 66717
(MICH); legit prope Tahquamenon Falls, Luce County, Michigan.
Illust. Text Figs. 810-812.
Pileus 2-3 cm broad, obtusely conic, becoming broadly conic, surface glabrous,
moist, hygrophanous, watery cinnamon buff moist, dingy pale pinkish buff faded.
Context brownish, fragile, odor and taste not distinctive, with FeSO4 no reaction.