The North American species of Psathyrella.

1972]

PSATHYRELLA

235

Stipe 3-4.5 cm long, 1.5-3 mm thick, equal, very fragile, white, pruinose above,
white floccose below from veil remnants, merely slightly brownish in base of stipe
in age.
Spores 7-8x 4.5-5 p, smooth, apical pore indistinct (apex rounded), shape in
face view broadly ovate to broadly elliptic, in profile broadly subovate to elliptic
(the ventral line slightly concave in some), color in KOH pale tawny but on
standing becoming pale cocoa-color, in Melzer's pale reddish tawny, wall about
0.3 pt thick.
Basidia 4-spored, 20-27 x 8-10 u, hyaline in KOH. Pleurocystidia scattered,
38-52 (-60) x 9-16 /, fusoid-ventricose, apex obtuse to acute, wall thin and smooth,
hyaline in KOH, content not distinctive in KOH or Melzer's. Cheilocystidia
similar to pleurocystidia but usually shorter, some vesiculose to clavate, small
cells also present. Caulocystidia versiform (Fig. 445), thin-walled, hyaline.
Pileus cuticle a layer of vesiculose cells 2-3 deep, the walls smooth, thin,
yellowish to hyaline in KOH, content not distinctive in either Melzer's or KOH.
Hyphae of context particularly in region of subcutis tawny in KOH, the walls
smooth, no distinctive reaction noted on any tissue in mounts revived in Melzer's.
Clamps present.
Type locality. Warren, Idaho County, Idaho.
Habit and habitat. Scattered on conifer duff, September.
Distribution. Known only from the type locality.
Observations. The spores of this species remind one of those of P. senex but
are pale tawny when first revived in KOH, and the basidiocarps are scattered on
the duff under conifers. It is not closely related to Agaricus cascus Fries, which
Fries in Epicrisis placed next to A. candolleanus. Drosophila pseudocasca
Romagnesi however is quite similar and a critical comparison with P. payettensis
should be made, but the latter has obtuse to subacute pleurocystidia whereas in
D. pseudocasca the neck is said to be scarcely different from the ventricose part.
193. Psathyrella harrisonii A. H. Smith, sp. nov.
Pileus 1-3.5 cm latus, late convexus, albo-squamulosus glabrescens, griseobrunneus; lamellae latae, confertae, brunneolae, demum fusco-brunneae; stipes
3-5.5 cm longus, 2-5 mm crassus, albidus, deorsum demum sordide brunneus;
fibrillosus, glabrescens; sporae 8-11 (-12) x 4-5 ~/; pleurocystidia 46-70 (-80) x
(8-) 10-18 ~, fusoidea vel fusoideo-ventricosa, acuta vel obtusa, subcrassotunicata
(tunica 0.6, crassa, in "KOH" griseo-vinacea vel hyalina). Typus. Harrison 7659
(MICH); legit prope Aylesford Lake, King County, Nova Scotia, Canada.
Pileus 1-3.4 cm broad, obtuse, expanding to broadly convex or nearly plane,
surface at first covered with small whitish squamules composed of fascicles of
outer-veil fibrils, margin fringed by fibrils also, glabrescent, moist and hygrophanous, dull gray-brown fading to dingy tan, striatulate when moist. Context thin
and fragile.
Lamellae broad, close, adnate, seceding, pallid brownish becoming rusty brown
and finally chocolate-brown, drying chocolate brown; edge white-fimbriate.
Stipe 3-5.5 cm long, 2-5 mm thick, hollow, fragile, slightly and evenly enlarged
downward, white but discoloring to brownish at least slightly, at first somewhat
fibrillose from veil remnants but soon glabrous.
Spores 8-11 (-12) x 4-5 it, smooth, apical pore distinct and spore apex slightly
truncate, shape in face view narrowly elongate-elliptic to oblong, in profile suboblong to obscurely inequilateral, color in KOH cocoa-brown becoming chocolatebrown, in Melzer's tawny, wall about 3,u thick.