North American species of Mycena.

382 NORTH AMERICAN SPECIES OF MYCENA

differentiated pellicle of narrow (3-4 1u) hyphae demonstrable on some
pilei (its hyphae serving to bind the vesiculose cells together), all parts
pale yellow in iodine.
Habit, habitat, and distribution.-Scattered to gregarious on damp
soil but particularly on partly buried pieces of bark of elm and hickory;
Tennessee, New York, and Michigan, also in Africa. Around Ann
Arbor, Michigan, the species is very abundant during the latter half
of June, when the weather is warm and showery.
Material studied.-Smith, 32-34, 32-248, 32-364, 32-458, 32-530,
717, 1313, 1377, 1394, 1414, 1481, 6372, 10233, 15096, September 5, 6,
1932, Michigan.
Observations.-According to my experience, the floccose appearance of the stipe is most noticeable on young carpophores. Many
hyaline caulocystidia are intermingled with those having brownish
content. In age nearly all the caulocystidia are hyaline, and many
collapse. When Murrill described M. atribrunnea, he undoubtedly
had old specimens in which the stipes had become glabrous.
The tendency of the pilei to split radially is correlated with their
structure. The pellicle is very poorly developed and is made up of
narrow hyphae which serve to bind together the large cells of the
hypoderm (these may appear to form a cuticle). The enlarged
hyphae forming the hypoderm are radially arranged and, of course,
separate readily when the slender threads of the binding hyphae
are not numerous.
In my tests on well-dried specimens no positive amyloid reaction
was observed on stipe, pileus, gills, or spores. Although M. floccipes
is a very distinct species, carpophores with glabrous stipes may be a
bit difficult to identify.
191. MYCENA ULMICOLA Smith
Mycologia, 31: 281. 1939
Illustrations:
Plate 89 A; Text fig. 46, nos. 6-7 (p. 381).
Smith, Mycologia, 31, figs. 1 L; 2 D, E (cystidia and spores).
Pileus 1-2.5 cm. broad, obtusely conic, becoming umbonate with
a flaring or recurved margin or sometimes nearly plane, with a narrow
sterile margin, which is curved in slightly at first but which soon
becomes straight and more or less lacerated and finally deeply split,
surface even to slightly rugose, translucent, striatulate on the margin