The North American species of Psathyrella.

1972]

PSATHYRELLA

59

(Fig. 64). Caulocystidia 40-65 10-18 pM, fusoid-ventricose with obtuse apex,
thin-walled, hyaline in KOH, readily collapsing.
Pileus with a cuticle of inflated cells 3-5 deep, their walls hyaline and
refractive in KOH, smooth, thin; content not distinctive in either KOH or
Melzer's. Tramal hyphae with hyaline smooth walls revived in KOH, content not
colored but in Melzer's the subhymenium reddish orange in places. Clamp
connections present.
Type locality. Ann Arbor, Michigan.
Habit and habitat. Cespitose around stumps of beech and locust (Robinia),
rare but found in quantity when it does fruit, late summer and fall.
Distribution. Michigan (Smith 20789 (Type), 20999, 38866).
Observations. This is a white, fibrillose species developing pinkish tints on the
pileus by late maturity, spores distinctly vinaceous-brown in deposit and very
narrow. It is not one of the annulate species.
24. Psathyrella subvolvata A. H. Smith & Hesler, Jour. Elisha Mitchell Soc. 62:
187. 1946.
Illust. 1. c. fig. 2. Text figs. 58-60.
Pileus 2.5 cm broad, obtuse, becoming broadly subumbonate, surface appearing dry because of a dense covering of innate long white fibrils which surround
the disc and become aggregated into fascicles, the margin incurved and striatulate
at first, glabrescent or nearly so part way to disc in age, entirely white at first
but becoming tinged umber as the spores mature. Context fragile, white,
hygrophanous, odor and taste not distinctive.
Lamellae close, broad (about 5 mm), shallowly adnexed, white, slowly becoming dark violaceous-brown ("benzo brown"), edges slightly paler and nearly even.
Stipe 2.5 cm long, 3 mm thick, equal except for the subbulbous base, white,
hollow, bulb surrounded by a white mass of fibrils which almost form a volva,
densely fibrillose over lower half, pruinose above.
Spores 6-7.5 x 3-3.5 /,, smooth, apical pore present but inconspicuous, shape in
face view oblong, in profile somewhat allantoid, color in KOH near snuff brown
(dull yellow-brown), in Melzer's ochraceous-tawny, wall 0.2 p thick.
Basidia 4-spored, 16-19 x 6-6.5 u; hyaline in KOH, slightly clavate but basal
portion not conspicuously narrowed. Pleurocystidia abundant, 28-36(-40) x 10 -12 (-14) A, utriform to broadly fusoid-ventricose with rounded apex, wall smooth,
thin and hyaline; cell content not distinctive in KOH or Melzer's. Cheilocystidia
similar to pleurocystidia or merely clavate, both types hyaline in KOH.
Gill trama of narrow parallel hyphae hyaline in KOH. Pileus trama of
compactly interwoven hyphae hyaline in KOH. Cuticle of pileus of hyaline
vesiculose cells in a layer irregularly 2-3 cells deep or if cells are very large (up
to 60 x 40 pu or more) only one cell deep, wall thin, smooth and hyaline, cell content
not distinctive. Filamentose hyphae 6-10, wide originating in the cuticle and
remaining appressed over the surface, the cells elongate, tubular and not disarticulating. Clamp connections present. No distinctive reaction on any tissue
when mounted in Melzer's.
Type locality. Indian Camp Creek, Great Smoky Mountains National Park,
Tennessee.
Habit and habitat. Solitary on soil along a trail.
Distribution. Known only from the type locality.
Observations. Psathyrella columbiana has much the same type of volva but
significantly larger spores and lacks innate fibrils on the pileus.