The North American species of Psathyrella.

1972]

PSATHYRELLA

379

observed). The above data are taken from one pileus. Cheilocystidia 20-35x
9-25 pt, clavate and with yellow mostly slightly thickened walls (-0.5 / thick),
some cystidioid cells also present on the edge.
Pileus cuticle a layer 1-3 cells thick of inflated smooth thin-walled (but
refractive in KOH) cells ochraceous as revived in KOH. Hyphae of subcuticular
region near clay color in KOH and with smooth walls (from a mature pileus).
Clamps present.
Type locality. Herman-Silver River, Baraga County, Michigan.
Habit and habitat. Cespitose to gregarious on very rotten wood and on debris,
July.
Distribution. Known only from the type locality.
Observations. The extremely variable pleurocystidia are distinctive in this
group, but the aspect of the basidiocarps is that of P. obtusata.
Material examined. Michigan: Ammirati 3310 (Type).
353. Psathyrella acuticystis A. H. Smith, sp. nov.
Pileus 2-3.5 cm latus, late convexus, sparse fibrillosus glabrescens, albidus
demum griseo-brunneus, ad marginem copiose fibrillosus; lamellae confertae,
latae, brunneolae demum fusco-griseae; stipes 2-4.5 cm longus, 2.4-4 mm crassus,
albo-fibrillosus, sursum annulato-zonatus, glabrescens, deorsum melleibrunneus;
sporae 6.2-7.5 x 3.5-4 a; pleurocystidia 42-64 x 9-16, fusoide ventricosa, ad
apicerum praeacuta, maura 0.5-0.6 /u crassa; fibulae adsunt. Typus. Smith 73875
(MICH); legit prope Upper Priest River, Idaho.
Illust. P1. 84, fig. b; Text Figs. 769-772.
Pileus 2-3.5 cm broad, obtuse to convex, expanding to broadly convex, surface
thinly coated with white fibrils at first, glabrescent, white when young but brownish to grayish tones evident as the spores mature, subhygrophanous and in age
very pale tan "pale pinkish buff" to "pinkish buff," margin at first heavily fringed
with white veil remnants. Context thin, fragile, watery pallid becoming pallid,
odor and taste not distinctive, with FeSO4 no color change.
Lamellae close, broadly adnate, broad, brownish pallid when young, soon gray
(near avellaneous) and finally "hair brown" (dark brownish gray), edges whitish.
Stipe 2-4.5 cm long, 2.4-4 mm thick, short, often curved, hollow and fragile,
densely white-fibrillose to an annular zone, fibrillose-pruinose over apical region,
becoming dingy honey-color beneath the veil remnants.
Spore deposit purple-fuscous. Spores 6.2-7.5x3.5-4 /g, smooth, apical pore
very inconspicuous to absent, shape in face view very obscurely (and bluntly)
fusiform to ovate, somewhat pointed at apiculate end, in profile obscurely
inequilateral, color revived in KOH chocolate-black, reddish in KOH at first on
fresh material, tawny-red in Melzer's, wall about 0.3 u thick.
Basidia 4-spored, 18-24x6-9 g, hyaline, clavate. Pleurocystidia abundant,
42-64x9-16 /A, fusoid-ventricose with sharply acute apex, wall refractive and
thickened to 0.5-0.6 gL in the ventricose part, very thin near the apex, hyaline and
smooth in KOH, content not distinctive in either KOH or Melzer's. Cheilocystidia
similar to pleurocystidia but usually smaller. Caulocystidia versiform: (1) elongate fusoid-ventricose and 50-110x 9-15 g, with acute apex, neck often flexuous,
wall thickened slightly near the base, hyaline in KOH and often more or less
crooked or contorted; (2) vesiculose to clavate and 10-17 g broad, wall thin to
thickened slightly.
Cuticle of pileus a layer one to two cells deep of inflated to pedicellate cells