The North American species of Psathyrella.

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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

[VOL. 24

29. Stipe 4-7 cm long; growing on grassland in arid regions; lacking a well developed
outer veil. 131. P. owyheensis.
30. Stipe 8-15 cm long. 31
30. Stipe 3-6(-8) cm long. 32
31. Spores 6.5-8(9) X 4-4.5 X 4-5 /. 132. P. verna.
31. Spores 8-11 X 5-6,u. 133. P. alnicola.
32. Pileus becoming pinkish after fading; cheilocystidia nearly all vesiculose
to clavate. 134. P. mesocystis.
32. Not as above. 33
33. Lamellae olive-brown when mature. 135. P. subfasciculata.
33. Lamellae grayish violaceous-brown. 34
34. Pleurocystidia acute to subacute, apex often with hyaline debris adhering.
121. P. lanatipes.
34. Pleurocystidia obtuse and smooth. 136. P. idahoensis.
103. Psathyrella peudolactea A. H. Smith, sp. nov.
Pileus 2-5 cm latus, obtuse conicus demum campanulatus, sparse fibrillosus;
glabrescens, ad marginem denticulatus, lactoalbus, demum melleibrunneus, saepe
rugulosus; lamellae angustae confertae albae demum griseo-brunneae; stipes
3-7 cm longus (3-)4-8(-10) mm crassus, dissiliens, fibrillosus, glabrescens, albidus demum melleus; sporae 6-7 x3-3.5 u; pleurocystidia 38-62 x 10-18 l,
fusoide ventricosa; ad apicerum acuta; fibulae adsunt. Typus. Smith 39799
(MICH); legit prope Pellston, Michigan.
Illust. Text Figs. 255-257.
Pileus 2-5 cm broad, obtuse with a bent-in margin, expanding to broadly
conic or umbonate and the margin spreading, surface moist and hygrophanous,
thinly coated with veil fibrils near the margin, the edge denticulate from remains
of submembranous veil material, color milk-white to watery white before spores
mature, as spores mature the color gradually becoming brown and at maturity
dingy honey brown, translucent striate moist, in age at times rugose-reticulate.
Context white becoming watery brownish by maturity, odor and taste not distinctive.
Lamellae close, narrow, ascending-adnate, white, becoming dark gray-brown
(lacking red tinges), finally near "wood brown," edges even.
Stipe 3-7 cm long, (3-) 4-8 (-10) mm thick, equal or enlarged downward,
hollow, splitting readily, surface rather coarsely fibrillose from veil but finally
glabrous, apex somewhat scurfy, white at first, dingy honey-color in age.
Spores 6-7 x 3-3.5 /, smooth, apical pore evident and causing apex to appear
truncate, shape in face view oblong to narrowly elliptic, in profile suboblong
to obscurely inequilateral, color in KOH cocoa-color darkening to chocolate, in
Melzer's reddish tawny, wall about 0.2 A thick.
Basidia 4-spored, 20-24x6-7 /, hyaline in KOH. Pleurocystidia abundant,
38-62 x 10-18 It, fusoid to fusoid-ventricose, the apex acute to subacute and often
remaining collapsed and usually coated with amorphous granules as an incrustation, hyaline, thin-walled, content not distinctive. Cheilocystidia similar to
pleurocystidia. Caulocystidia as the terminal cell of a chain of 2-4 cells of
cortical hyphae, all of the cells inflated, the end cell mostly vesiculose to clavate
and 12-20 pt broad.
Pileus cuticle a layer of greatly inflated vesiculose cells with yellowish hyaline,
smooth walls and no distinctive content. Subeuticular region brownish as first
revived in KOH but soon fading to yellowish or nearly hyaline; tramal body
hyaline in KOH, the hyphae smooth. Clamps present. No distinctive reactions
in Melzer's on any tissue.