North American species of Mycena.

16 NORTH AMERICAN SPECIES OF MYCENA

has been employed here with some hesitation to distinguish M. aurantiidisca Murrill from M. Adonis (Fr.) Quelet. The distinction in this
instance is questionable because there are apparently no correlated
differences. The colors belong to the same series of reds and appear
to be nothing more than extreme variations in intensity.
MACROSCOPIC CHARACTERS OF THE SURFACE OF BOTH PILEUS AND STIPE
In thin-fleshed agarics like Mycena the gill outlines often show
through the moist, somewhat translucent flesh of the pileus as conspicuous radially arranged lines or striations, and the cap is then
described as "translucent-striate." Although the character is usually
mentioned in descriptions, it is of distinctly secondary importance
from a taxonomic standpoint. The amount of moisture present has
much to do with determining whether the striations are obscure or
conspicuous, and they usually disappear as the pileus fades. Pilei
are frequently characterized by rather distinct radial wrinkles or folds
and are then described as "sulcate-striate." In some larger species,
such as M. parabolica, these are quite distinctive. They are much
more frequently found in the very small species, however, and here
they usually represent a somewhat faded condition, their development
being correlated with the loss of moisture from the pileus. To be of
any value, the character should be observed on young fresh specimens
at the time of collection. In a few Mycenae, small as well as large,
the pileus is irregularly wrinkled, particularly around the disc. This
condition is described as "rugulose," and is exceedingly variable in
most species, including M. marginella var. rugosodisca. It is illustrated for M. niveipes, Plate 68, and should be regarded as a secondary
character. In M. niveipes the wrinkles frequently disappear as the
pileus expands.
The character of the surface of the pileus is readily classified in
three categories: dry, moist, and viscid. Representatives of the
first group are rare. In general, those species with numerous pilocystidia or fibrils over the cap have a rather dry appearance. This is
typical for M. delicatella and is an important diagnostic feature.
However, by far the majority of the species fall into the second group,
and hence, because of the frequency of its occurrence, the character
of moistness is of secondary importance to the taxonomist. Most of
the members of this group show a distinct change in their appearance
with loss of moisture and are said to be "hygrophanous." As a rule,
the fragile species fade quickly, thus accentuating the change in ap