North American species of Mycena.

100 NORTH AMERICAN SPECIES OF MYCENA

than 0.5 mm. thick, equal or the base flanged slightly, strigose, the
remainder pruinose like the pileus, chalky white over all.
Spores 8-11 X 5-6 qu, ellipsoid, hyaline, smooth, distinctly amyloid;
basidia four-spored; pleurocystidia present but buried in the hymenium and difficult to locate, 22-30 X 5-9 g, narrowly fusoid-ventricose
or some with irregular walls; cheilocystidia very conspicuous, forming
a sterile band, 36-62 X 6-12,, somewhat fusoid to subcylindric or
nearly filamentous, hyaline, the walls often irregular; gill trama
homogeneous, yellowish in iodine, hyphae slender; pileus trama
homogeneous beneath a turflike covering of upright pilocystidia and
filamentous projections, the pilocystidia 32-46 X 8-12 A, clavate to
ventricose, the apex often subcapitate, filamentous cells 3-4 g thick,
branched or variously contorted, no incrustations seen; caulocystidia
similar to pilocystidia, stipe tissue vinaceous brown in iodine.
Habit, habitat, and distribution.-Scattered on debris of red alder
and thimbleberry; Kalaloch, Washington. Known only from the
type locality.
Material studied.-Smith, 13035.
Observations.-This fungus resembles small forms of M. delicatella
in stature and in the flexibility of the pileus and stipe, but the spores
separate it at once by both their shape and amyloid reaction. The
stipe is not separable from the pileus, and its base is not truly bulbous;
hence the species cannot be referred to Pseudomycena. The broad,
well-formed gills distinguish it from the preceding species having
amyloid spores. There are other differences as well, such as spore
size and the nature of the hairs and cystidia covering the pileus.
From the species in Kiihner's section Lacteae it differs in its amyloid
spores and stipe tissue.
32. Mycena pusillissima (Pk.), comb. nov.
Omphalia pusillissima Peck, Bull. New York State Mus., 116: 27. 1907.
Omphalopsis pusillissima Murrill, North Am. Flora, 9: 311. 1916.
Illustration: Text fig. 5, no. 6 (p. 81).
Pileus 1-2 mm. broad, conic to convex or somewhat cucullate,
the disc flattened or slightly depressed, glabrous, pure white and
opaque, not striate, membranous, odor and taste not distinctive;
lamellae very distant, 3-5 reach the stipe, decurrent, white, becoming
foldlike and often disappearing before reaching the margin of the
pileus; stipe 1 cm. long, filiform, glabrous, hyaline white, inserted on
the substratum.