North American species of Mycena.

EUMYCENA: ADONIDAE

157

Omphalia nitrosa Kauffman, Pap. Mich. Acad. Sci., Arts, and Letters, 11: 202.
1930.
Omphalia delectabilis Smith, Bull. Torr. Bot. Club, 64: 482. 1937.
Prunulus leucophaeus Murrill, North Am. Flora, 9: 336. 1916.
Mycena leucophaea Murrill, Mycologia, 8: 220. 1916.
Illustrations:
Plate 8 A; Text fig. 14, nos. 7, 10 (p. 154).
Peck, Ann. Rep. New York State Mus., 27, pl. 1, figs. 22-25.
Pileus (3) 8-20 mm. broad, obtusely conic with an appressed
margin at first, sometimes campanulate, becoming broadly conic to
broadly campanulate, sometimes papillate, the margin usually spreading in age, watery white at first or the disc with a faint watery-gray
cast, almost chalk white when faded or in age a bit yellowish around
the disc; flesh very thin and very fragile, white, taste hardly distinctive, odor strongly nitrous or nearly lacking (sometimes evident only
if the flesh is crushed); lamellae arcuate at first and soon becoming
long-decurrent, subdistant to distant, narrow, white, edges even or
fimbriate; stipe 2-4 cm. long, 0.5-1.5 (2) mm. thick, equal, nearly
filiform at times, fragile-cartilaginous, tubular, base white-strigose
and apex faintly pruinose, otherwise glabrous and naked, white.
Spores 5-7 X 3.5-4 u, subellipsoid, smooth, nonamyloid; basidia
four-spored; pleurocystidia scattered to abundant, 33-58 X 7-12 y,
fusoid-ventricose, elongating to subcylindric or nearly filamentous
at times (usually in age), hyaline, smooth; cheilocystidia similar to
the pleurocystidia, numerous; gill trama homogeneous, pale yellow in
iodine; pileus trama homogeneous beneath a thin pellicle, the hypoderm not differentiated, all parts yellowish in iodine.
Habit, habitat, and distribution.-Scattered to gregarious on needle
beds under conifers, particularly around and under fallen treetops or
heaps of dead branches, not uncommon during the late summer and
fall in wet weather. It has been found in New York, Idaho, Washington, Oregon, and California in the United States and in Nova
Scotia and Ontario in Canada.
Material studied.-Smith, 788, 904, 1065, 2784, 3391, 4562, 7770,
7931, 8021, 8497, 8623, 8815, 8921, 14464, 14497, 14510, 16752. Atkinson, 13491 (as M. leptocephala). Gruber, Oregon. Kauffman,
two collections from Oregon (as Omphalia nitrosa). Slipp, UIFP:
2601, 2674.
Observations.-The small, moderately broad spores, cystidia on
both faces and edges of the gills, the nitrous odor, and obtuse pileus