The North American species of Psathyrella.

216

MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

[VOL. 24

173. Psathyrella pallida A. H. Smith, sp. nov.
Pileus 10-25 mm latus, circa 2 cm altus, conicus, candido-fibrillosus vel subgranulosus, glabrescens, sordide albidus demum ad centrum dilute argillaceus;
lamellae albidae demum cacaocolor, confertae, latae; stipes 2-3 cm longus, 1.5 -2.5 mm crassus, albidus, fibrillosus, glabrescens; sporae 6.5-7.5 x 4-4.5 /; pleurocystidia 34-57x9-15 /, fusoide ventricosa, ad apicerum acuta; fibulae in hyphis
stiparum. Typus. Smith 53359 (MICH); legit prope Riggins, Idaho.
Illust. Text Figs. 393, 394.
Pileus 10-25 mm broad and about 2 cm high, broadly conic, surface at first
snow-white from a granular-fibrillose coating of superficial veil remnants, margin
fringed at first, soon glabrescent over all and dull white but with a "pale pinkish
buff" (pale buff) disc at times, not changing in appearance appreciably from
moist to faded condition. Context very fragile, white, odor and taste not
distinctive.
Lamellae white when young, becoming cocoa-brown, close, ascending,
moderately broad, edges even.
Stipe 2-3 cm long, 1.5-2.5 mm thick, equal or enlarged downward, hollow,
fragile, white, at first with superficial white fibrils as remnants of the veil and
extending to a superior fibrillose zone which finally is obliterated, glabrescent,
pruinose above the veil line, not discoloring appreciably in age or where handled.
Spores 6.5-7.5 x 4-4.5 /, smooth, apical pore present but apex only obscurely
truncate; shape in profile subovate, the plage area at most only slightly flattened,
in face view elliptic to ovate, color in KOH cinnamon-ochraceous, in Melzer's pale
tawny, wall about 0.2 /A thick.
Basidia 4-spored, 18-24x 7-8 /J, hyaline in KOH. Pleurocystidia abundant,
34-57x 9-15,/, fusoid to fusoid-ventricose with acute apex, thin-walled, hyaline,
walls rigid (many cystidia broken cleanly near the base), content not distinctive
in KOH or Melzer's. Cheilocystidia similar to pleurocystidia but usually smaller.
Caulocystidia not found but veil hyphae often in the form of chains of ellipsoid
cells or short more or less uninflated cells some of which disarticulate. Cuticle of
pileus a layer of inflated cells 15-30 /i wide, with smooth hyaline walls revived in
KOH and no colored zone beneath the cuticle. Scattered pileocystidia project
from the cellular cuticle, the cystidia 28-40 x 8-14 /, clavate to fusoid-ventricose.
No amyloid or fleeting amyloid reaction present on any tissue of the basidiocarp.
Clamp connections readily found on hyphae of the stipe.
Type locality. Seven-Devils Mountains, Nezperce National Forest, Idaho.
Habit and habitat. On debris in mixed woods (alder and conifers), September.
Distribution. Known only from the type locality.
Observations. The distinguishing features of this species are the cocoa-brown
colored spores, veil material of wide short cells at times disarticulating, acutely
pointed pleurocystidia, short relatively broad spores, white pileus and copious
veil. In this species we find the initials of the differentiation of subgenus
Cystopsathyra. When we have learned more about the genus, we shall probably
have demonstrated that the progression to Cystopsathyra is a gradual one with
a number of intermediate species.
Stirps Frustulenta
Psathyrella sect. Frustulentae (Romagn.) Singer, Sydowia 15: 68. 1961.
Key to the Species of Stirps Frustulenta
1. Spores ochraceous to rusty brown when first mounted in KOH. 2
1. Spores in KOH cocoa-brown or darker. 3