North American species of Mycena.

MURRILL'S SEMITROPICAL SPECIES

469

tinct natural group which has certain characters in common with the
M. euspeirea complex. I did not find gelatinous layers over the
stipes, however, and the subgelatinous trama indicates a progression
away from Mycena toward Heliomyces. 0. convexa, 0. myceniformis,
0. roriduliformis, and 0. subavellanea may all belong in one species.
The differences Murrill used to separate them do not appear significant. The spore size he has given for myceniformis is incorrect.
In roriduliformis he probably observed spores suspended in the mount
and consequently, because of their small size, failed to orient them
properly and hence erroneously described them as subglobose.
OMPHALIA PETASIFORMIS Murrill
Mycologia, 8: 220. 1916
Omphalopsis petasiformis Murrill, North Am. Flora, 9: 316. 1916.
"Pileus hat-shaped, with a large and prominent umbo, solitary,
2 cm. broad, 1 cm. high; surface pure-white, glabrous, faintly striate,
the umbo faintly straw-colored: lamellae decurrent, distant, broad,
thin, ventricose, pure-white: stipe cylindric, equal, smooth, glabrous,
pure-white, 3 cm. long, 2-3 mm. thick."
Type collected on ground under tree ferns, Morce's Gap, Jamaica.
The single carpophore appears to be typical of the white Mycenae.
The tramae of the pileus and gills are each homogeneous and not
otherwise distinctive. Pleurocystidia and cheilocystidia are not
differentiated. The basidia are two-spored and have prominent
sterigmata. The spores measure 11-14 X 5.5-7,, are hyaline in
KOH, smooth, and yellowish in iodine. In the size of the spores this
species appears to be quite similar to M. McMurphyi, but it is apparently distinct by virtue of its larger size and slightly smaller spores on
two-spored basidia. When the four-spored form of 0. petasiformis
is found, its spores should be smaller, and the difference in spore size
between these two should thus be sharper than is indicated by the
published measurements.
OMPHALIA SUBSCYPHOIDES Murrill
Mycologia, 8: 220. 1916
Omphalina subscyphoides Murrill, North Am. Flora, 9: 348. 1916.
"Pileus convex, depressed at the center, solitary, reaching 13 mm.
broad; surface dull-white, smooth, glabrous, margin irregular, con