North American species of Mycena.

168 NORTH AMERICAN SPECIES OF MYCENA

three collections, Oregon, Idaho, Wyoming. Mains, 5024. Overholts, 19382; July 20, 1914, Colorado. Slipp, UIFP: 1528, 3089.
Observations.-When growing under conifers the base of the stipe
is hardly curved and is covered with a thin mat of white mycelium or
scattered hairs; when growing in oak woods the stipe is often decidedly curved at the base and has a rootlike strigose portion which
may extend for some distance under the leaves. I regard this difference as one caused by the nature of the habitat. Only one collection
from under oak was made in Michigan, but the species was very
abundant at Lost Creek, Oregon (just west of McKenzie Pass).
Two forms were found there, each growing in troops of several hundred carpophores. One had a yellow cap at all stages. The other
was characterized by buttons with pinkish pilei, which by the time
they matured faded to pale yellow or retained a slight pinkish tinge
around the disc. In age the two forms were indistinguishable. Josserand (1930) has found a somewhat similar situation in Europe.
Kuiihner (1938) has used the name M. floridula for this reddish form,
and I must admit the difference in color appears to be constant. The
impression one gets from collecting these two together, however, is
that at best one is just a variety of the other. M. amabilissima Peck
is very distinct from the pink variety of M. flavoalba not only in its
brighter colors but also in the manner in which they fade from red to
white-not yellow.
My specimens of the pink variety of M. flavoalba did not have
colored gills at first, and they differ in this respect from M. floridula
of Josserand and Ktihner.
74. MYCENA FLAVOALBA var. microspora, var. nov.
Pileus 5-15 mm. latus; stipes 2-4 cm. longus, 1-1.5 mm. crassus;
sporae 5-6 X 3 a.
In all other respects the collection resembled typical material.
The specimens were found September 8, 1941, at Park Creek, 1000
feet elevation, Mt. Baker, Washington. A. H. Smith 16753-type.
The specimens were growing gregariously under conifers (pine, hemlock, and Douglas fir). Since the spore size of M. flavoalba has been
remarkably constant in all my other collections, it appeared advisable
to segregate this material. It occurred in considerable quantity,
and the spore size was constant. Slipp, UIFP: 3565, has collected it
in Idaho.