The North American species of Psathyrella.

1972]

PSATHYRELLA

267

Lamellae only moderately close, broad, ascending-adnate, slightly toothed,
faces pallid gray and gradually becoming evenly chocolate-gray, edges even and
whitish.
Stipe 2-4 cm long, 1-2 mm thick, equal, hollow, fragile, pruinose over all at
first, finally naked, hyaline grayish white above, basal region dull dingy brown in
mature basidiocarps but not distinctly discoloring when broken or bruised.
Spores 11-13.5x 6.5-8.5 /, smooth, apex truncate from a distinct apical pore,
shape in face view elliptic to slightly ovate, in profile subovate to nearly elliptic,
color in KOH blackish brown becoming dark chocolate-color (grayer), in Melzer's
bay-red, wall about 1 M thick.
Basidia 4-spored, clavate, subcapitate, hyaline in KOH, 18-24 x 10-15 /A.
Brachybasidioles present by late maturity. Pleurocystidia very rare, 24-32
(-40) x 9-14 p, fusoid-ventricose with acute apex; wall thin, smooth and hyaline;
cell content not distinctive in KOH or Melzer's. Cheilocystidia similar to pleurocystidia or clavate to saccate and 26-40 10-16 p. Caulocystidia present as
filaments.
Gill trama thin, pallid brownish revived in KOH. Pileus trama sordid yellowish brown in KOH. Cuticle of pileus of vesiculose cells in a layer about one cell
deep; wall thin, smooth and hyaline; cell content not distinctive in KOH or
Melzer's. Clamp connections present. No distinctive reaction noted on any tissue
in Melzer's.
Type locality. Ann Arbor, Michigan.
Habit and habitat. Scattered on manured soil.
Distribution. Known only from type locality.
Observations. The caulocystidia require further study preferably from fresh
material. The filaments noted on the stipe as revived in KOH could have been
fibrils from a rudimentary veil, though this is not likely as some were seen to
originate from hyphae of the cortex.
227. Psathyrella prona (Fries) Gillet, Les Hymen. 618. 1874.
Agaricus pronus Fries, Epicr. Syst. Mycol. 239. 1838.
Coprinarius prona (Fr.) Quelet, Enchir. Fung. 120. 1886.
Psathyra prona (Fr.) Lange, Flora Agar. Danica 4: 101. 1939.
Illust. Gillet, 1. c., pl., 589. Lange, 1. c. pl. 155, fig. C & C'. P1. 78, fig. e; Text
Figs. 520-522.
Pileus 6-12 mm broad, up to 15 mm high, ovoid, becoming obtusely conic or
campanulate, glabrous except for scattered fibrils over the marginal area at first,
margin soon glabrescent, translucent striate, smooth and sordid "buckthorn
brown" when moist, the marginal area soon "wood brown," hygrophanous, fading
to "avellaneous" or paler over all, atomate and somewhat rugulose when faded,
sometimes tinged pinkish along the margin or over all in age. Context very thin
and fragile, concolorous with the pileus when moist or faded, odor and taste not
distinctive.
Lamellae ascending adnate, subdistant (about 15 reach the stipe) very broad
(about 3 mm), pale grayish brown when young, becoming "benzo brown" to
"fuscous" at maturity, edges white-fimbriate at first, often pinkish when mature.
Stipe 3-6 cm long, 1-1.5 mm thick, equal, hollow, very fragile, hyaline white
to "tilleul buff" or more grayish toward the base, with very thin evanescent
patches of veil remnants below, soon glabrescent, base slightly strigose, apex
pruinose.