North American species of Mycena.

EUMYCENA: CORTICA TAE

385

been able to locate a sclerotium. The brown-edged denticulate gills,
blackish to dirty-brown color, scurfy stipe, and pseudorhiza distinguish the species macroscopically. This is the M. denticulata of
Kauffman in the Agaricaceae of Michigan.
SECTION CORTICATAE
The species of this section have the cuticle formed by a palisade
of clavate or enlarged cells instead of the usual pellicle of narrow
radially arranged hyphae. In one species the spores are amyloid.
The fungi of the previous section approach those included here to
some extent, but there is a fundamental difference in the organization
of the cuticle. In the species of the previous section the pellicle is
poorly developed, and the hypoderm may thus appear to be the cuticle
and to be made of vesiculose hyaline cells. In radial sections these
cells are seen to be considerably elongated and to occur as segments of
filaments, whereas in the Corticatae the cells which actually form the
cuticle present the same appearance regardless of whether the sections
of the cap are radial or tangential.
KEY TO SPECIES
1. Spores amyloid............................. 193. M. hymenocephala
1. Spores nonam yloid............................................. 2
2. Spores 6-7.5 X 3.5-4 i................ 195. M. wyomingensis
2. Spores 5-6 X 4.5-5.5,................ 194. M. ludoviciana
193. Mycena hymenocephala (Smith), comb. nov.
Collybia hymenocephala Smith, Pap. Mich. Acad. Sci., Arts, and Letters, 926:
61. 1941.
"Pileus 2-3 cm. broad, convex or obtuse when young, the margin
at first incurved, broadly convex to plane in age, glabrous, 'olivebrown' to 'buffy brown' when fresh, hygrophanous, fading to
'tilleul buff' (whitish), or more olivaceous gray, atomate and glistening when faded, not striate; flesh concolorous with the surface in
moist or faded condition, thin, very soft and fragile, odor not distinctive, taste slightly farinaceous; lamellae depressed-adnate but
toothed, subdistant (18-20 reach the stipe), 2-3 tiers of short individuals, moderately broad (2.5-3 mm.), 'tilleul buff' or becoming
darker and grayish in age, edges slightly uneven; stipe 4-5 cm. long,