The North American species of Psathyrella.

1972]

PSATHYRELLA

85

KOH. Pileus with a cuticle of vesiculose cells one to two cells deep, the walls thin,
smooth and hyaline, the content not distinctive. Hyphae of the context of greatly
enlarged cells hyaline and smooth in KOH.
Type locality. Jalapa, Mexico.
Habit and habitat. Solitary on the ground in woods.
Distribution. Mexico (type studied), Texas (Thiers 1396).
Observations. The relationships of this species are clearly in this group but
more data on the veil, if one indeed is present, is needed.
46. Psathyrella thiersii A. H. Smith, sp. nov.
Pileus 1.5-3 cm latus, conicus demum campanulatus, ad marginem appendiculatus, glaber, spadiceus vel subspadiceus; sapor farinaceus; lamellae confertae
demum subdistantes, angustae, luteolae demum "avellaneus"; stipes 5-8 cm longus,
2.5-4 mm crassus, albus, glaber; sporae 5-6.5(-7.5) x 3-4.2 rx; cheilocystidia 33 -50x 11-16,; fibulae adsunt. Typus. Thiers 1866 (MICH); legit prope Richards,
Texas.
Pileus 1.5-3 cm broad, conic to convex becoming subconic to campanulate,
margin incurved when young, becoming straight to flared when older, appendiculate with white veil elements when young, becoming glabrous with age, surface
moist, glabrous, frequently becoming striate when older, when young dark brown
("bister") on the disc, changing to brown or olivaceous-brown ("snuff brown" to
"tawny-olive") toward the margin, when older sometimes fading to yellowish or
in age finally darkening to blackish brown ("mummy brown"). Context thin,
brittle, concolorous with the surface, taste farinaceous, odor not distinctive.
Lamellae ascending-adnate, close to subdistant, narrow, thin, yellowish ("light
buff") when young becoming lavender gray ("avellaneous" to "wood brown")
when older; margin entire, concolorous with the faces, no lamellulae present.
Stipe 5-8 cm long, 2.5-4 mm thick at apex, tapering slightly toward the apex,
stuffed to hollow, surface dry, glabrous when young, frequently becoming
fibrillose when older, white during all stages of development.
Spores 5-6.5 (-7.5) x 3-4.2 u, smooth, germ pore indistinct, shape in face view
oblong to elliptic, in profile more or less elliptic, color in KOH smoky umber
slowly becoming nearly hyaline, in Melzer's pale reddish tawny, wall thin.
Basidia 4-spored, 13-17 x 8-10 /, clavate, hyaline in KOH. Pleurocystidia not
differentiated. Cheilocystidia abundant, 33-50x11-16 p, subcylindric to fusoidventricose, apex obtuse to broadly rounded, wall thin, smooth and hyaline, cell
content not distinctive in KOH or in Melzer's. Caulocystidia similar to
cheilocystidia, scattered.
Gill trama hyaline, interwoven, of filamentous hyphae about 5 jt wide. Pileus
trama honey brown to dark honey brown ("buckthorn brown"), the hyphal walls
smooth or practically so. Cuticle of pileus a palisade of clavate to vesiculose
cells with walls thin, smooth and hyaline, cell content not distinctive. Clamp
connections present.
Type locality. Near Richards, Texas.
Habit and habitat. Gregarious to scattered on humus near hardwood logs.
Distribution. Texas.
Observations. In the light of species concepts as proposed in this work and as
currently used in Europe, this fungus is a distinct species in its own right and
I take pleasure in dedicating it to its collector. The dark colored pileus, yellowish
young lamellae, spores which slowly become nearly hyaline on standing for an