The North American species of Psathyrella.

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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

[VOL. 24

Psathyrella subg. Mycophila A. H. Smith, subg. nov.
Crescunt parasitice in Coprini. Typus Psathyrella epimyces.
Since a parasitic mode of existence is so unusual in this genus it appears
logical to me to recognize any species which have made this adjustment at the
above level. Only the type species is known to me.
25. Psathyrella epimyces (Peck) A. H. Smith, comb. nov.
Agaricus epimyces Peck, Rep. N. Y. State Mus. 35: 133. 1884.
Stropharia epimyces (Peck) Atkinson, Plant World 10: 128. 1907.
Stropharia coprinophila Atkinson, Jour. Mycol. 8: 118. 1902.
Illust. Atkinson, 1907, fig. 23, 24. P1. 22; P1. 23, fig. b; Text Figs. 73, 74.
Pileus 2-6 cm broad, ovoid to globose when young, becoming broadly convex
to nearly plane, the margin sometimes elevated in age, surface silky-fibrillose, not
hygrophanous, white but becoming sordid in age, margin fibrillose-appendiculate
when the veil breaks. Context thick, soft, white or whitish, odor and taste not
distinctive.
Lamellae narrowly adnate or at times somewhat adnexed, narrow, broadest
toward the pileus margin, thin, pallid at first, soon blackish brown and as dried
blackish, the edges white-fimbriate.
Stipe 2-7 cm long, 5-15 mm thick, fleshy, equal or tapering upward, stuffed
solid but becoming hollow, soft, floccose-mealy, striate, white-annulate near the
base or not, or veil remnants appearing volva-like.
Spore deposit blackish. Spores 7-9(-10) x4-5 /,, smooth, apical pore not
distinct, shape in face view ovate to elliptic, in profile subelliptic to very obscurely
inequilateral, color in KOH dark chocolate-color, in Melzer's bay-brown; wall
0.7-1 g thick.
Basidia 4-spored, 24-34 (-48) x 7-9 g, clavate, pedicel often long and flexuous,
hyaline in KOH, merely yellowish in Melzer's. Pleurocystidia 40-64(-70) X9 -15 It, broadly fusoid-ventricose with obtuse apex varying to subcylindric with
rounded apex, pedicel often distinctly elongated, wall thin, smooth and hyaline
as revived in KOH, cell content not distinctive in either KOH or Melzer's.
Cheilocystidia similar to but smaller than the pleurocystidia and more of them
with an obtuse to subacute apex. Caulocystidia, none located (only dried material
studied for this feature).
Gill trama cellular near the base of the gill, of elongated narrow subparallel
hyphae near the edge, hyaline in KOH, subhymenium very narrow and indistinct.
Pileus with a rudimentary cuticle of pear-shaped to clavate, hyaline cells, the
cells 20-42 x 10-20 /u, some upright, some decumbent and in some sections appearing as a layer of vesiculose cells with hyaline filamentous hyphae projecting from
the layer. Clamp connections regularly present. No distinctive reactions on any
part as revived in KOH or Melzer's, cell walls all smooth and thin.
Type locality. North Greenbush, New York.
Habit and habitat. On Coprinus comatus.
Distribution. United States: Michigan, Minnesota, New York and Wisconsin.
Canada: Ontario.
Observations. The relatively thick-walled spores lacking a readily observable
germ pore, the silky pileus and the parasitic habit set this species apart from
other Psathyrellae, but the parasitic habit is the most unusual feature. Similar
probable "accidents" of a parasitic habit of this kind are Boletus parasiticus
on Scleroderma and Volvariella surrecta on species of Clitocybe. In the latter