The North American species of Psathyrella.

1972]

PSATHYRELLA

95

Illust. P1. 16, fig. a; Text Figs. 139, 140.
Pileus 2.5-7 cm broad, obtusely conic when young, either remaining conic or
the margin flaring, sometimes becoming broadly campanulate, at times finally
nearly plane, glabrous or with a few scattered fibrils near the margin, margin at
first appendiculate with a veil which is membranous to submembranous and
breaks up to form patches of tissue, glabrescent over all in age, when young and
fresh "cinnamon-drab" to "avellaneous," at times becoming nearly "cinnamonbrown" before becoming sordid livid brown as the spores mature, hygrophanous,
fading to sordid "ochraceous-buff" or "tilleul buff" (whitish), surface faintly
striate when moist, lubricous to subviscid and smooth, somewhat atomate when
faded. Context thin concolorous with the surface, firm and not markedly fragile,
odor and taste mild.
Lamellae ascending adnate to horizontally adnate (old pilei), readily seceding,
close to crowded (36-40 reach the stipe), narrow to moderately broad, equal,
whitish when young becoming "hair brown" or in age finally nearly black, edges
even.
Stipe 9-16 cm long, 3-6 mm thick, equal or the base slightly enlarged, hollow,
cavity large, rigid, strict, fragile, white, surface with minute appressed white
fibrils when young, soon glabrous except for the pruinose apex, sometimes striate
above.
Spores 12-15x 6.5-8 /, smooth, apical pore broad but not conspicuous, shape
in face view elliptic to ovate, in profile subelliptic to obscurely inequilateral, color
in KOH fuscous but slowly darkening to dark chocolate-color, in Melzer's bayred, wall about 0.5-0.7 x thick.
Basidia 20-25 x (7-)8-12 a, 4-spored, hyaline in KOH, subcapitate. Pleurocystidia none. Basidioles varying to brachybasidioles in age, 16-20 x8-15 /.
Cheilocystidia 30-42 x 8-12 / (rarely 17 u), subcylindric to ventricose, apex obtuse, wall thin, smooth and hyaline, content not distinctive in KOH or Melzer's.
Caulocystidia in patches, subcylindric to fusoid-ventricose with obtuse apex,
40-75 x 9-18 a, wall thin, smooth and hyaline, cell content not distinctive.
Pileus with a cuticle of vesiculose cells 3-4 cells deep, their walls thin, smooth
and hyaline, the cell content not distinctive in KOH or Melzer's. Hyphae of
the trama hyaline in KOH and merely yellowish in Melzer's. Clamps present.
Type locality. Elwha Lake, Olympic National Park, Washington.
Habit and habitat. Scattered to gregarious on humus, spring.
Distribution. Idaho, New Mexico, Washington.
Observations. This species, first misidentified as P. longipes, features terete
spores, an essentially glabrous pileus when young (save for a few fibrils near the
margin), and both a relatively firm pileus and broader gills. Drosophila involuta
has the same spore size, but is given as in "loco ambusto" and has a copious outer
veil. The two appear very close, however.
Material examined. Idaho: Smith 69082, 69095. New Mexico: Barrows
905. Washington: Imshaug 1960; Smith 3318 (Type), 14097, 14163, 14166, 14250,
14406, 14409, 14535, 14536, 14580, 30411, 30478, 30567, 30685.
55. Psathyrella thomii A. H. Smith, sp. nov.
Pileus 2-3 cm latus conicus demum campanulatus ad marginem fibrillosus,
glabrescens, albus demum fusco-brunneus; lamellae adnatae subdistantes angustae, pallidae demum purpureo-pruinosae; sporae 15-18x 10-12,; pleurocystidia
30-52 x 10-20,/; fibulae adsunt. Typus. Thom 15 Jan., 1924 (MICH); legit Chas.
Thom, Louisiana.