The North American species of Psathyrella.

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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

[VOL. 24

Habit and habitat. On dead elm stumps and logs, October.
Distribution. Michigan.
Observations. The distinguishing features of this species are the pale pigmentation of the basidiocarps, presence of both thin-walled pleurocystidia and
some with slightly thickened walls, the large caulocystidia, the dark chocolatecolor of the spore deposit, the pileus cuticle containing so many clavate pedicellate cells and the medium-small spores. It appears to be close to P. cernua, a
European species.
Material examined. Michigan: Potter 10297; Smith 78300 (Type).
339. Psathyrella melleipallida A. H. Smith, sp. nov.
Pileus 10-15 mm latus, late convexus, melleus demum pallidus, glaber; lamellae angustae confertae, albidae, demum brunneo-grisseae, in exsiccatis fuscae;
stipes 2-3 cm longus, 1-1.5 mm crassum, albidus, sparse fibrillosus; spores
8-10x 5-6 t/; pleurocystidia 38-56 x 12-16 /, pediculato-elliptica vel late ventricosa; fibulae adsunt. Typus. Potter 6424 (MICH); legit prope Ithaca, Michigan.
Illust. Text Figs. 733-736.
Pileus 10-15 mm broad, obtuse becoming broadly convex, moist and hygrophanous, more or less honey-color and fading to pallid (tilleul buff) or with a residual
flush of cinnamon, pallid when dried; veil thin, fibrils at first near or along the
margin but soon evanescent. Context very thin and delicate.
Lamellae narrow, close, adnate, white at first but gradually becoming brownish gray (near "wood brown"), mature gills pale fuscous as dried, edges even.
Stipe short, 2-3 cm long, 1-1.5 mm thick, equal, fragile, white, with scattered
fibrils over the lower part at first, glabrescent, not discoloring appreciably and
unicolorous as dried.
Spores 8-10x5-6 /i, smooth, truncate from a distinct apical pore, shape in
face view elliptic to obscurely ovate, in profile subelliptic to obscurely inequilateral, color in KOH cocoa-color when first revived in KOH and slowly becoming
chocolate-gray, in Melzer's reddish tawny, wall about 0.5 / thick.
Basidia 4-spored, clavate, 18-21x6-9 /k, hyaline in KOH. Pleurocystidia
scattered, 38-56 x 12-16 /, in optical section elliptic beyond a narrow basal
pedicel, varying to fusoid-ventricose with a short neck and broadly rounded apex,
wall thin, smooth and hyaline, cell content not distinctive in KOH or Melzer's.
Caulocystidia scattered, 28-52 x9-14 /, fusoid-ventricose with obtuse apex or
subcylindric with flexuous walls and apex obtuse to subacute, small clavate cells
also present, all hyaline, smooth and thin-walled.
Gill trama regular, the hyphae pale brownish to hyaline as revived in KOH.
Pileus trama with brown smooth to faintly roughened walls in the subcuticular
region (in KOH). Cuticle a layer of vesiculose cells one to two deep and hyaline
in KOH. Clamps present.
Type locality. Ithaca, Michigan.
Habit and habitat. Gregarious on old logs and surrounding leaf mold at
bottom of a dried up pond.
Distribution. Michigan.
Observations. The pale honey-colored pileus, narrow close gills, white stipe
and relatively broad spores are distinctive.