The North American species of Psathyrella.

1972]

PSATHYRELLA

397

Basidia 4-spored, 20-28x9-12 /. Pleurocystidia scattered, 40-58(-62) x
10-14 a, fusoid-ventricose, apex obtuse to acute and some forked into two nipplelike protuberances, wall hyaline, thin and smooth, cell content not distinctive,
wall of neck often flexuous as revived in KOH. Cheilocystidia clavate and short,
12-18x 10-14 pu, abundant, hyaline in KOH or yellowish at the base. Caulocystidia scattered, 20-40 x6-15 a, clavate, ventricose or various odd shapes,
smooth, thin-walled, hyaline, numerous lens-shaped refractive thickenings present in the cells of the hyphae of the stipe cortex (these are appressed against the
inner wall).
Gill trama ochraceous in KOH or in old pilei hyaline. Pileus trama ochraceous
in KOH in old pilei, rusty brown in young ones but fading on standing to hyaline.
Cuticle of pileus a palisade of clavate to ellipsoid cells with pale ochraceous to
hyaline walls (in KOH). Clamp connections present.
Type locality. Lower French Creek, Medicine Bow Mountains, Wyoming.
Habit and habitat. Gregarious on burned over areas.
Distribution. Wyoming.
Observations. There was no true pseudorhiza in this species even though the
stipes were sunken appreciably in the soil.
373. Psathyrella deserticola A. H. Smith, sp. nov.
Pileus 1-2.5 cm latus, late convexus vel expanso-umbonatus, glaber, castaneus;
lamellae brunneolae, demum rufo-fulvae, confertae demum subdistantes, latae;
stipes 2-3.5 cm longus, 1-1.5 mm crassus, deorsum brunneus, glaber; velum sparsissimum; sporae 7-9 x 5-6 (-6.5) A; pleurocystidia 28-45 x 9-15 /, fusoide ventricosa, acuta vel subacuta; fibulae adsunt. Typus. Smith 64950 (MICH); legit
Ellen Trueblood, in Owyhee County, Idaho.
Illust. Text Figs. 754-757.
Pileus 1-2.5 cm broad, broadly convex, expanding to plane or with a low umbo,
surface glabrous, moist, hygrophanous, dark chestnut-brown to cinnamon-brown
when moist, dull tawny and opaque when faded. Context thin, fragile, odor and
taste not distinctive.
Lamellae dull brownish when young, near "Mars brown" at maturity (deep
rusty brown), adnate, soon seceding, close to subdistant, broad, edges even.
Stipe 2-3.5 cm long, 1-1.5 mm at apex, whitish above, dull brownish below,
naked or with only a few fibrils present, base white mycelioid.
Spore deposit dark rusty brown ("Mars brown"). Spores 7-9x5-6(-6.5) a,
smooth, apical pore broad and apex more or less truncate, shape in face view
broadly elliptic, a few broadly ovate, in profile subelliptic (the suprahilar area
flattened to depressed slightly), color in KOH tobacco brown (near "Prout's
brown"), reddish tawny in Melzer's, wall about 0.5 I thick.
Basidia 4-spored, 8-9 t broad, clavate. Pleurocystidia scattered, 28-45 x
9-15 a, fusoid-ventricose, neck short and apex acute to subacute, hyaline, smooth,
wall rigid and 0.3-0.4 u thick, content not distinctive in KOH or Melzer's. Cheilocystidia 24-37 x8-13 A, clavate to mucronate or fusoid-ventricose, hyaline,
smooth, thin-walled. Caulocystidia versiform (Fig. 757), 18-38 x9-15 pu, fusoidventricose to clavate or elliptic, thin-walled, smooth, hyaline.
Pileus with a cuticle of a layer of vesiculose cells 2-3 cells deep and with
yellowish walls in KOH, the lower cells with some rusty brown pigment incrustations (in KOH). Hyphae of the subcuticular region a layer with inflated to
tubular cells having dark dusty brown walls in KOH, the pigment incrustations