North American species of Mycena.

390 NORTH AMERICAN SPECIES OF MYCENA
lacking an elongated pedicel; gill trama of narrow compactly arranged
hyphae, yellowish in iodine; pileus trama with a cuticle of a palisade
of clavate cells 22-35 X 8-10 i, their contents dark smoky brown,
hyaline thin-walled pilocystidia project at intervals from the palisade
and measure 30-50 X 7-10 u, tramal body homogeneous, composed
entirely of compactly arranged narrow hyphae, yellowish in iodine;
caulocystidia 40-70 X 7-10,u, subcylindric, hyaline, thin-walled;
stipe tissue yellowish in iodine.
Habit, habitat, and distribution.-Cespitose on rotten wood under
spruce and fir, June, 1938; University of Wyoming Science Camp,
10,000 feet elevation. Known only from the type locality.
Observations.-This species is very closely related to Mycena trichoderma Josserand in Kuihner, but differs in the more compact palisade
layer over the pileus, the cespitose habit of growth, rooting stipe, and
smaller spores. The spores do not turn distinctly yellowish in iodine,
as happens in many species with nonamyloid spores. M. lenta Maire
is also rather closely related but is said to be rimose, as in certain
species of Inocybe, and to lack pleurocystidia. In addition, its colors
are apparently more brownish. In Kiihner's classification M. wyomingensis would fall in the group Spuriae if the spores were amyloid.
SECTION HYDROPUS
Mycena brevipes is placed here because of the numerous lactifers
in the trama of the pileus and gills. It is not known whether the
species has a colored or a hyaline latex or, for that matter, any latex
at all. KI(hner has suggested that this group ought to be considered
a distinct genus, and Singer has recognized it as such. I have seen
fresh specimens of only M. marginella and M. umbrina and, on the
basis of these species and var. rugosodisca of M. marginella, am not inclined to make such a distinction. M. atroalboides, which has a rather
copious juice at times, is also keyed out here, but is related to species
in the Typicae.
KEY TO SPECIES
1. Gill edges sordid brownish...................... 198. M. marginella
1. Gill edges concolorous with faces................................ 2
2. Cheilocystidia regularly echinulate or apices covered with short rodlike protuberances........................... 135. M. atroalboides
2. Cheilocystidia smooth or intermediate between rough and smooth
ty p e s...................................................... 3