The North American species of Psathyrella.

1972]

PSATHYRELLA

437

Spores 9-12 x 5.5-6.5,u, smooth, apical pore present as a hyaline spot, shape
in face view oblong to obscurely ovate, in profile slightly bean-shaped to subelliptic; color in KOH cocoa color soon becoming chocolate gray to darker.
Basidia 4-spored, 9-12 p wide, hyaline. Basidioles clavate. Pleurocystidia
scattered, 32-48 x 10-14 u, fusoid-ventricose with obtuse to subacute apex, smooth,
thin-walled, content not distinctive. Cheilocystidia mostly clavate to utriform,
up to 17 p broad, hyaline, smooth and thin-walled.
Cuticle of pileus of vesiculose cells to about 35 t wide, hyaline, thin-walled,
2-3 cells deep, surface-cells often giving rise to a cystidium-like projection which
may elongate into a hyphal proliferation. Trama adjacent to cuticle with some
cells having colored wall thickenings or incrustations. Clamps present.
Habit, habitat and distribution. Two together on muck in a swamp, Cedar
Lake, Washtenaw County, Michigan, October 20, 1971, Smith 81028.
Observations. This variant is too close to the type of P. salictaria to justify
describing it as new. No willow was in the habitat and the stipe was not brown
but otherwise the Michigan collection appears to belong to this species.
(See) 389. Psathyrella seymourensis (variant Smith 81044)
Pileus 8-20 mm broad, obtusely conic with a straight margin, expanding to
broadly conic to campanulate, rarely convex, surface moist and hygrophanous,
when young with scattered fibrils from a thin outer veil but these soon evanescent,
remaining as a slight fringe (or small patches near the margin) for a longer time,
color pale to medium cinnamon brown but soon a chocolate-gray brown as spores
mature, fading over marginal area first to chocolate gray (a paler shade than when
moist), atomate when faded. Context exceedingly thin and fragile odorless, taste
not distinctive.
Lamellae broadly adnate, subdistant, ascending, broad, grayish cocoa-color to
"cinnamon drab" at maturity, merely brownish when young, edges whitish.
Stipe 1-3 cm long, 1-1.5 mm thick, equal, pallid above, honey-color below,
thinly fibrillose below or fibrils aggregated into minute patches or squamules,
glabrescent and dingy in age, very fragile.
Spores 7-9 x 4-5 /, smooth, apical pore present as a hyaline spot but apex not
truncate or only obscurely so in a few spores, shape in face view oblong to elliptic,
rarely obscurely ovate, in profile elliptic to very obscurely inequilateral, color in
KOH chocolate-brown, somewhat near bister on standing, tawny to pale bay in
Melzer's.
Basidia 4-spored, hyaline, broadly clavate. Basidioles broadly clavate. Pleurocystidia 36-50x 10-15 /u, ventricose with a short to long narrowed neck to a
subacute apex, smooth, thin-walled, hyaline (both the wall and the content).
Cheilocystidia similar to pleurocystidia but neck often shorter, some clavate cells
present. Caulocystidia basically similar to cheilocystidia but wall often more
refractive in KOH and possibly swelling more as revived, neck sometimes forked.
Pileus cuticle a layer of cells 3-4 thick, walls thin, pale cinnamon to nearly
hyaline in KOH, smooth. Hyphae of trama adjacent to cuticle, pale to medium
cinnamon in KOH, or entire trama this color, color located in the wall (some
incrustations also present). Clamps present but inconspicuous and often rare.
Habit, habitat and distribution. On waste sandy soil near scattered clumps
of grass and patches of Polytrichum. It occurs solitary to scattered after heavy
rains in the fall at the time when Amanita muscaria reaches the peak of its fruiting
cycle.