The North American species of Psathyrella.

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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

[VOL. 24

subliberae, sublatae (2-2.5 mm) demum subdistantes ad acierum crenulatae;
stipes 2.5-4 cm longus, 1.5-2 (-3) mm crassus, deorsum brunneolus, sparse fibrillosus, glabrescens; velum parvum; sporae 8-10.5x 5-6 /; pleurocystidia 38-47x
6-15 pt, fusoide ventricosa, subcapitata vel 6-10 /j lata et subcylindrica; fibulae
adsunt. Typus. Wells-Kempton 7/4/64 no. 1 (MICH); legit prope Katmai
National Monument, Alaska.
Pileus 9-15(-35) mm broad, obtuse to campanulate or finally nearly plane,
the margin decorated with thin patches of fibrils at first, rarely umbonate in age,
glabrous, smooth, hygrophanous, bright chestnut to auburn brown at first, fading
to dingy cinnamon-buff, when moist translucent striate nearly halfway to disc.
Context concolorous with the surface either moist or faded, moderately thick for
size of pileus (about 2 mm), odor and taste not distinctive.
Lamellae pallid in buttons, becoming grayish brown and finally deep blackish
brown, ascending adnate to nearly free, moderately broad (2-2.5 mm), close
becoming subdistant, edges obscurely pallid and crenulate.
Stipe 2.5-4 cm long, 1.5-2 (-3) mm at apex, nearly equal, pale dingy tan inside
and out in lower half, pallid-pruinose punctate above, with scattered pallid long,
appressed fibrils from the thin veil lower down, somewhat mycelioid at the base;
veil thin and pallid, evanescent.
Spores dark violaceous-brown in deposit, 8-10.5 x 5-6 /, smooth, apical pore
distinct causing apex to be slightly truncate, shape in face view broadly elliptic
to somewhat ovate, in profile subelliptic to obscurely bean-shaped, color in KOH
medium chocolate-color, soon going to dark chocolate-color, in Melzer's reddish
tawny, wall 0.5 p thick.
Basidia 18-24x5-7 /, 4-spored, clavate, hyaline. Brachybasidioles not differentiated. Pleurocystidia scattered, 38-47 x 6-15 /, fusoid-ventricose with obtuse
to almost rounded apex (dumbbell-shaped at one extreme) or narrow (6-10 p
wide) and subcylindric (the two types intergrade), wall thin, smooth and hyaline
in KOH or Melzer's, cell content not distinctive in either medium. Cheilocystidia
24-60 x 7-13 J, elongate, subcapitate to fusoid-ventricose with obtuse apex, thinwalled, hyaline in KOH, smooth; some clavate cells larger than basidioles are also
present. Caulocystidia more or less similar to the pleuro- and cheilocystidia.
Cortex hyphae hyaline in KOH but with numerous particles of highly refractive
amorphous debris in the cells.
Gill trama with a central strand rusty brown in KOH but fading, subhymenium
of inflated cells near the base of the gill, some cells with refractive amorphous
particles. Cuticle of pileus a poorly formed layer of somewhat inflated cells
2-3 deep (those at surface collapsing readily). Hyphae of the subcutis yellowbrown in KOH but walls smooth or practically so, cells often with particles of
refractive debris (in KOH or Melzer's). Clamps present.
Type locality. Katmai National Monument, Alaska.
Habit and habitat. Gregarious on volcanic ash and soil with a thin carpet of
moss present, July.
Distribution. Alaska.
Observations. This is a rather distinctive species by virtue of the wide spores
for their length, variable shape and width of the pleurocystidia, thin but distinct
veil, and the large amounts of refractive debris present in the hyphae of stipe and
pileus when the tissues are revived in KOH.
Material examined. Alaska: Wells-Kempton 7-4-64 no. 1 (Type), 6-19-65
no. 1.