The North American species of Psathyrella.

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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

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Illust. Text Figs. 549-551.
Pileus 1-3.5 cm broad, obtusely conic with a straight margin, expanding to
plane or with a low umbo, surface moist and hygrophanous, "Rood's brown"
to "Hay's brown" dark vinaceous-brown when moist, fading to vinaceous-pallid
or a dingy pinkish tan, in age the margin brighter pink as in P. gracilis but in
some the margins not changing, the disc pinkish buff, at first with a thin coating
of white fibrils over the marginal half, soon glabrescent, the edge naked, surface
in age often wrinkled. Context fragile, quickly gray in KOH, taste mild, odor
metallic-disagreeable but not strong.
Lamellae vinaceous-buff when young, then vinaceous-brown and finally
chocolate-brown or darker, adnate-seceding, broad, close to nearly subdistant,
broad, edges whitish.
Stipe 3-7 cm long, 2-3.5 cm thick, equal, fragile, undulating, hollow, at first
tinged vinaceous, white at maturity or in age, white fibrillose over lower part,
apex faintly so, not discoloring at base but merely finally dingy over all in age;
veil not leaving a zone or ring on stipe when it breaks.
Spores 14-16 x 5.5-7.5 /, smooth, with an apical hyaline pore often at a
slight angle (not truly apical), in profile elliptic or nearly so, in face view
elliptic to slightly ovate, fuscous in KOH (many pale ones present), in Melzer's
dark reddish brown, wall about 1, thick.
Basidia 4-spored, 12-15 i broad, clavate. Pleurocystidia voluminous, 46-80
x 12-25 tu, elliptic pedicellate to ovate-pedicellate to fusoid-ventricose, neck
7-10 / wide in elongated cells, apex rounded or obtuse, wall thin and smooth,
cells mostly remaining partly collapsed. Cheilocystidia similar to pleurocystidia
but smaller and varying to fusoid. Caulocystidia near apex of the stipe closely
resembling the cheilocystidia, rare lower down. No distinctive reactions were
noted on mounts made of any tissue in Melzer's.
Pileus cuticle of voluminous cells 15-50,u wide, some with a broad pedicel,
walls smooth, hyaline to brownish in KOH, the layer 2-3 cells deep or if cells
are 50-70 /, long only 1-2 cells deep. Subcuticular region dingy vinaceous-brown
in KOH, fading slowly. Clamps present.
Type locality. Ann Arbor, Michigan.
Habit and habitat. On chip-dirt of elm, May.
Distribution. Known only from the type locality.
Observations. The slight veil, dark vinaceous-brown pilei, vinaceous tinge
in the stipe at first, large spores and voluminous pleurocystidia are distinctive.
In these features as well as in the colors of the basidiocarps the species is very
close to P. barlae but the vinaceous-brown KOH reaction of the pileus trama in
P. pseudocorrugata and the gray KOH reaction of the fresh context appear
sufficient to distinguish them.
258. Psathyrella caespitosa Peck, Bull. Torrey Club 34: 348. 1907.
Pileus 1.5-2.5 cm broad, convex to subumbonate, surface striate to disc or
subsulcate near the margin, grayish brown to fleshy-gray. Context thin, taste
farinaceous.
Lamellae thin, subdistant, adnate, cinereous, becoming black or blackish
brown.
Stipe 6-7 cm long, 2-3 mm thick, slender, hollow, mealy and white at the
top, brownish below.
Spores 14-19(-20) x 7-9(-10) /, smooth, obscurely truncate from a small but