The North American species of Psathyrella.

1972]

PSATHYRELLA

335

Stipe 4 cm long, 1 mm thick, rather fragile, filiform, smooth, snow-white,
mycelioid at the base.
Spores 10-13 x 6-7 Iu, smooth, truncate from a broad apical pore, shape in face
view very broadly elliptic, in profile elliptic to very obscurely inequilateral, color
in KOH dark chocolate-color in a short time, in Melzer's dark tawny red, wall
about 0.8 /A thick.
Basidia 4-spored, hyaline in KOH, 18-22 x 9-11 A. Pleurocystidia scattered,
36-44x 10-14 g, fusoid-ventricose with obtuse to subacute apex, neck becoming
more elongated in age, wall thin, smooth and hyaline, cell content not distinctive
in KOH or Melzer's. Cheilocystidia either similar to pleurocystidia or clavate
to ellipsoid or saccate, 18-28x9-15 / for the inflated types. Caulocystidia not
studied.
Pileus having a cuticle of inflated hyaline cells 1-3 deep, some large clavate
cells present indicating an arrangement in an irregular palisade. Context hyphae
brown in KOH. Clamps present.
Type locality. Motzorongo, Mexico.
Habit and habitat. Solitary on humus.
Distribution. Known only from the type locality.
Observations. The snow-white stipe and very broad ellipsoid spores are its
most distinctive features.
305. Psathyrella calvinii A. H. Smith, sp. nov.
Pileus 5-10 mm latus, conicus vel campanulatus, rufofulvus, glaber; lamellae
confertae demum subdistantes, latae, brunneolae demum atro-brunneae; stipes
2-5 cm longus, circa 1 mm crassus, glaber, pallidus, deorsum demum brunneus;
sporae 12-15 x 7-8 (13-16 x 7-8.5) /u; pleurocystidia 36-52 x 10-16 /t, fusoide ventricosa, acuta; fibulae adsunt. Typus. Kauffman 9-9-23 (MICH); legit prope
Centennial, Wyoming.
Illust. Text Figs. 655, 656.
Pileus 5-10 mm broad, obtusely conic becoming obtusely campanulate, glabrous, moist, color "russet" when young but becoming cinnamon-brown before
changing to grayish brown ("buffy brown") as spores mature, hygrophanous and
fading to pale tan ("cinnamon-buff") or over marginal area avellaneous, atomate
when faded. Context very thin and fragile, concolorous with the surface either
moist or faded; odor and taste not distinctive.
Lamellae close becoming subdistant, moderately broad to broad, broadly
adnate but readily seceding, brownish at first but becoming blackish brown by
maturity, edges entire and not distinctively colored.
Stipe 2-5 cm long, about 1 mm thick, slender, fragile, equal, glabrous, whitish
to pallid but finally brownish over all, sparingly fibrillose in button stages from
the remains of a rudimentary veil.
Spores 12-15 x 7-8,u (13-16 x 7-8.5, on 2-spored basidia), smooth, apical pore
distinct but apex obscurely to distinctly truncate (in largest spores), shape in face
view oblong to elliptic, in profile subelliptic to obscurely inequilateral, color in
KOH date brown becoming "mummy brown" or blacker, in Melzer's reddish
tawny, wall about 1.2 p thick.
Basidia 2- or 4-spored, 24-32 x 10-14 pi, clavate, hyaline or at the base the wall
pale tawny. Pleurocystidia rare to scattered, 36-52 x 10-16 f, ventricose with a
narrow neck tapered to a sharp pointed apex, wall thin, smooth and hyaline, cell
content not distinctive in KOH or Melzer's. Cheilocystidia similar to pleuro