North American species of Mycena.

2 NORTH AMERICAN SPECIES OF MYCENA

The work of classifying any group of agarics consists of two phases.
The first is concerned with the recognition of the various species as
they occur in nature and the variations they exhibit from year to
year or in different habitats. The second has to do with the nomenclature, and it is here that one encounters the greatest difficulties.
Neither Atkinson nor Kauffman made a thorough study of the nomenclature formany of the species. Because American investigators saved
the type specimens of the new species they described, it has. been
possible to ascertain the microscopic details now considered essential
in delimiting a species, and thus avoid the confusion of concepts that
has characterized European agaricology since the time of Fries. However, since many American students did not pay close attention to
microscopic details, numerous misidentifications have appeared in our
literature, and a multiplication of names for some species has resulted.
Besides the need for more detailed information on the characters
of American Mycenae, the question of the limits of the genus was
also very pertinent because of some disagreement among investigators
over the position of many "borderline" species. Thanks to the work
of Ktihner (1938), the limits of the genus have now been made much
more precise. Although the arrangement presented here differs in
some particulars from that of Kiihner, it is in close agreement with
his.
DEFINITION OF MYCENA
In his most widely used work Fries (1874) considered Mycena a
subgenus of Agaricus and described it as follows (p. 129): "...stipes
fistulosus, cartilagineus. Pileus submembranaceus, plus minus striatus, primitus conico- 1. parabolico-cylindricus ob marginem primitus
rectum, stipitem sursum attenuatum amplectentem 1. parallelo-adpressum. Lamellae haud decurrentes (tantum denticulo uncinatae).
Epiphyti 1. radicati, graciles, subcampanulati, vix umbilicati."
Kihner (1938) has given the following detailed characters of the
genus: Carpophores gymnocarpic (always?), small, slender, delicate,
putrescent; hyphae with clamp connections, with nonaeriferous intercellular passages, the pigment in general vacuolar. Pileus thin, submembranous, more or less translucent striate or sometimes plicate,
very often conic, campanulate or furnished with a pointed mammillate
umbo, the margin at first straight or more rarely somewhat incurved.
Flesh of pileus with the upper hyphae generally short and inflated
(the hypoderm). Covering of the pileus with superficial hyphae