North American species of Mycena.

DIAGNOSTIC CHARACTERS

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white to pale yellowish. Very faded (hence whitish) specimens of
M. niveipes usually dry whitish, but young, unfaded carpophores
which are dark gray will retain this color in drying, and hence in some
cases one must learn to recognize the variation in the appearance of
dried specimens just as one learns to recognize color variations of
fresh carpophores. Dried material, of course, is of greatest value in
studies of the microscopic characters.
MICROSCOPIC CHARACTERS
Readers interested in the anatomical details of the various types
of fruiting bodies grouped in Mycena should consult Kuhner's (1938)
excellent account. The present discussion is limited to the characters
I have emphasized in the arrangement and description of species in
order to avoid needless repetition.
Spores
Size; shape and markings, and reaction to iodine (Melzer's reagent)
are of major importance in recognizing species. Spore size should be
determined from spore deposits taken from perfectly fresh fruiting
bodies. My favorite method is to place a cap, gills down, on a glass
slide for five, ten, or twenty minutes and then to measure the spores
that have been discharged. In following this procedure one should
always remember that, as the cap becomes wilted, the discharged
spores are likely to be atypical. The length of the spores of the
various species ranges from as low as 3-4 At to 15-18.t. The majority
have spores 6-11, long. Slight differences in spore size and shape,
such as those existing between M. amicta and M. subcaerulea or
between M. galericulata and M. hemisphaerica, have been used to distinguish species only after many collections have been studied and the
differences have been found to be constant. Where they are not
distinctive, as in M. capillaripes and its forms, they have not been
emphasized. This creates an apparent inconsistency in the text,
but I believe the difficulty is one that needs to be elucidated by culture
work and mating experiments rather than by continued field observations. Arnold (1935) showed that in Marasmius elongatipes Peck
long- and short-spored forms were interfertile. Such a study as this
should be made for M. subcaerulea and M. amicta.
Shape is also an important character. If one examines the line
drawings in the text figures, he will note that the more or less ellipsoid