North American species of Mycena.

EUMYCENA: DEMINUTIVAE

131

Bresadola, Icon. Mycol., 5, pl. 249, fig. 1.
Fries, Icon. Sel. Hymen., 1, pl. 82, fig. 4.
Pileus 4-8 mm. broad, obtusely conic to convex, soon broadly
conic to campanulate, the margin straight at first but sometimes
flared in age, surface glabrous and moist, translucent-striate to the
disc, pale vinaceous brown, sordid brown, or grayish brown, paler
grayish or sordid brown when faded, becoming sulcate; flesh very
thin and delicate, odor and taste not distinctive; lamellae adnate,
subdistant, moderately broad, whitish or tinged grayish, edges pallid
or very faintly brownish; stipe 1.5-4 cm. long, 0.5-0.75 mm. thick,
equal, tubular, very weak, glabrous or a few white fibrils around the
base, concolorous with the pileus.
Spores 9-14 X 5-7 (8), ovoid to ellipsoid, amyloid, smooth;
basidia two-, three-, or four-spored; pleurocystidia not differentiated;
cheilocystidia 34-68 X 9-15 u, abundant, fusoid-ventricose to clavate,
smooth, hyaline; gill trama with a thin pellicle, the remainder of vesiculose cells, vinaceous brown in iodine.
Habit, habitat, and distribution.-Scattered on sod in pastures or
in open stands of conifers during the summer and fall; Michigan,
Washington, and California. I have found it only after periods of
heavy rain.
Material studied. -Smith, 33-596, 3273, 3753, 8493, 13996, 15984.
Observations.-The specimens of this species are very similar in
stature to M. sanguinolenta as it occurs in sphagnum bogs in Michigan. As yet I have not found M. debilis in great quantity, and have
not been able to answer certain questions in regard to some of its
characters. In the specimens seen the spore size and shape were
extremely variable. This was caused, no doubt, by the different
number of spores borne on the basidia. It is quite apparent, however, that spores from four-spored forms will be found to measure
8-11 J long. The colors of the pileus shade over into vinaceous,
and cause the fruiting bodies to resemble closely those of M. capillaripes. The situation is further complicated by a form of M.
capillaripes with large spores on two-spored basidia. Its gill edges
are usually colored, but at times this coloring is very inconspicuous.
Such forms differ from M. debilis in the presence of pleurocystidia
and in having a sharp acidulous odor emitted by the crushed flesh.
Observations on more abundant material should be made to determine
whether pleurocystidia are ever present in M. debilis and whether