The North American species of Psathyrella.

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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

[VOL. 24

P. filamentosa represent a stirps or "collective species"; but the differences presented here should not simply be disregarded. Studies of cultured material would
be highly desirable.
301. Psathyrella gracilis (Fries) Quelet, Champ. Jura et Vosges 152. 1872.
Agaricus gracilis Fries, Syst. Mycol. 1: 299. 1821.
Prunulus gracilis (Fr.) S. F. Gray, Nat. Arr. Brit. P1. 1: 630. 1821.
Coprinarius gracilis (Fr.) Kummer, Fiihr. Pilzk. 68. 1871.
Drosophila gracilis (Fr.) Quelet, Enchir. Fung. 119. 1886.
Psathyra gracilis (Fr.) Bertrand, Bull. Soc. Mycol. Fr. 17: 277. 1901.
Agaricus torpens var. leucophaeus Fries, Icon. Hymen. 2: 37. 1877.
var. gracilis
Illust. Fries 1. c., pl. 138, fig. 1. P1. 80; P1. 93, fig. a; Text Figs. 643, 644.
Pileus 1.5-3.5 (-5) cm broad, obtusely conic when young, the margin appressed
against the stipe, becoming broadly campanulate, convex or nearly plane, sometimes remaining obtusely conic, surface glabrous, smooth, polished, somewhat
lubricous when young, margin translucent striate when moist and frequently
becoming crenate or sulcate-striate, sometimes scalloped, the surface often more
or less rugulose in age, hygrophanous, pale buff to clay color ("cinnamon-buff"
to "clay color") when young, gradually becoming pallid and then lead-color as
the spores mature, fading to whitish or pallid, the disc often retaining a buff tinge,
in age frequently developing a pinkish hue at least along the margin. Context thin,
soon fragile, concolorous with the surface, odor and taste mild.
Lamellae moderately broad (4-6 mm), close, 22-25 reach the stipe, about
2 tiers of lamellulae, ascending adnate to horizontally adnate with a decurrent
tooth depending on the degree of expansion of the pileus, pallid when young
(tilleul buff), becoming dull purple-brown ("benzo brown") in age, edges even,
in age both the faces and edges or only the edges sometimes tinged pink.
Stipe 6-12 cm long, 1.5-3 mm thick, equal, strict, hollow, fragile, dull whitish,
faintly pruinose to fibrillose-pruinose above, smooth, glabrous downward or very
slightly fibrillose and soon glabrescent, veil absent or very rudimentary, base
often with white radiating strigose hairs and at times somewhat rooting but no
pseudorhiza present, at times the surface longitudinally striate.
Spore deposit dark chocolate-brown. Spores (10-) 11-14 (-15) x 6.5-8 n,
smooth, with a distinct apical pore causing the spore apex to appear slightly
truncate, shape in face view oblong to elliptic to weakly ovate, in profile obscurely
inequilateral to subelliptic, color in KOH chocolate-brown to (slowly) dark
chocolate-color, in Melzer's dull vinaceous-brown to dull bay (duller than in most
species), wall about 1.25 A thick.
Basidia 4-spored, 27-36 x 10-12 n, hyaline in KOH, abruptly clavate to
pedicellate-subcapitate, the enlarged part projecting somewhat at the time of
sporulation. Pleurocystidia very abundant, 54-75 x 10-16,u, subaciculate to
fusoid-ventricose, apex acute to subacute, the neck often flexuous, wall thin,
smooth and hyaline in KOH, cell content not distinctive in KOH or Melzer's.
Cheilocystidia shorter and more obtuse than the pleurocystidia and often yellowish as revived in KOH, occasional clavate cells also present. Caulocystidia
resembling the cheilocystidia but with some sphaero-pedunctulate cells 30-40 [
wide present, their walls thin and smooth, cell content not distinctive.
Gill trama of more or less regularly arranged hyaline hyphae, the subhymenium cellular but only a narrow band, hyaline or nearly so in KOH. Pileus trama