The North American species of Psathyrella.

1972]

PSATHYRELLA

199

relation to P. gracilis, but lists it as a synonym of P. microrhiza, a species I have
not recognized from North America. The original concept of P. microrhiza Lasch
as copied by Saccardo (Sylloge Fung. 5: 1073) states of the pileus "Pileo...
primitus luteo-piloso..." which to me indicates clearly that the species has a
yellow veil. It also had close narrow gills. On the basis of these characters I
do not accept the current concepts of P. microrhiza.
157. Psathyrella abortiva A. H. Smith, sp. nov.
Pileus 1-2 cm latus, conicus demum subplanus, copiose albo-fibrillosus vel
squamulosus, glabrescens, albidus demum fulvus; lamellae subdistantes, adnatae,
latae (3-4 mm), albidae demum brunneolae dein purpureo-brunneae; stipes
3-4 cm longus, 3-3.5 mm crassus, copiose fibrillosus, glabrescens; ad basem cum
carpophoroidiis; sporae 9-11(-12) x4.5-6(-7) ~a; pleurocystidia 32-48x8-12 a,
fusoide ventricosa, obtusa; fibulae adsunt. Typus. Smith 33-1099 (MICH); legit
prope Whitmore Lake, Michigan.
Illust. P1. 58 figs. a, b; Text Figs. 348-351.
Pileus 1-2 cm broad, obtusely conic, becoming convex and finally nearly plane,
the margin appressed against the stipe at first, pure white when young, becoming
"ochraceous-tawny" with a russet tinge while moist, hygrophanous, fading to a
dull ochraceous-buff, when young covered by a dense layer of white fibrils, at
maturity covered by recurved or erect fibrillose scales, margin fringed, in age
nearly glabrous, not striate. Context thin, white, fragile, odor and taste none.
Lamellae narrowly adnate, seceding, subdistant, moderately broad (3-4 mm),
white to sordid brownish when young, gradually becoming dark purplish brown.
Stipe 3-4 cm long, 3-3.5 mm thick, hollow, very fragile, equal, at first densely
covered by a white fibrous coating of recurved fibrillose scales, slowly glabrescent,
apex fibrillose to pruinose; numerous soft, fleshy, pallid carpophoroids 2-7 mm in
diam. occur in the vicinity of the basidiocarps or attached to them.
Spores 9-11(-12) x4.5-6(-7) A, smooth, apical pore distinct but small and
apex not truncate, shape in face view elliptic to ovate or in largest spores the
apical region snoutlike, in profile subelliptic to obscurely inequilateral, color in
KOH very soon dark chocolate-color, in Melzer's deep tawny-red, wall about
0.3-0.4 x thick.
Basidia 4-spored, 26-28x8-10 u, hyaline in KOH, clavate. Pleurocystidia
scattered to rare, 32-48x8-12 A, fusoid-ventricose, the apex obtuse, wall thin,
smooth and hyaline, content of cell not distinctive in either KOH or Melzer's.
Cheilocystidia similar to pleurocystidia or with longer necks, 36-52x8-14 p,>
obtuse, wall not colored in KOH. Caulocystidia clavate, scattered, 40-65x 4 -20 A, not infrequently with a "false clamp" (Fig. 351) wall thin, smooth and
hyaline, cell content not distinctive.
Gill trama with a narrow central strand of elongated cells bordered on each
side by large inflated cells, hyaline in KOH and weakly yellowish in Melzer's.
Pileus having a cuticle of hyaline vesiculose cells several deep, the walls thin,
smooth and hyaline, cell content not distinctive. Hyphae of the context perfectly
hyaline in KOH. Clamp connections present. No distinctive reactions on any
tissue when mounted in Melzer's.
Type locality. Whitmore Lake, Michigan.
Habit and habitat. Gregarious on very rich humus in elm and soft maple
swamps.