North American species of Mycena.

218 NORTH AMERICAN SPECIES OF MYCENA

from localities around Ann Arbor. It is a most variable fungus in all
four of its distinguishing characters: color of cap, type, of cheilocystidia, color of gill edge, and spore size. Nevertheless,, it is one of
the easiest Mycenae to recognize both in the field and in the herbarium.
The eheilocystidia are extremely variable. The drawings in text
figures 24, nos. 1-2 (p. 216), and 25, no. 8 (p. 223), were made from
sections of a single pileus. In some collections the smooth fusoidventricose type is most common or is the only kind present, whereas
in other collections a generous mixture of all types is present. The
age of the fruiting bodies must be taken into account when one is
studying the cystidia of this species. In mature or old pilei the
cheilocystidia are more irregular than they are in young individuals.
My comments on the variation in the shape of the cystidia are based
on a study of freshly matured caps in order to avoid the possible error
of comparing merely the different stages of development. The
pleurocystidia are not sufficiently numerous to be taxonomically
significant.
A distinct correlation between the color of the carpophores and
the amount of light in the habitat has been found. Out in the open
the fruiting bodies are very dark brown and have sordid-brown gill
edges. In the deep shade of conifer thickets a very pale delicate
yellow to whitish form is found. The majority of the fruiting bodies
collected in moderately open stands are intermediate between the
extremes noted above and form the bulk of the collections examined.
The color of the gill edges varies with the color of the pileus. In
dark forms they are sordid yellowish brown, whereas in pale forms
they are scarcely margined at all. If one uses a hand lens on the pale
form, one can nearly always find some gills with colored edges.
Bisby and others (1938) have briefly commented on a form (under
the name M. chlorantha) which appears to be very close to M. citrinomarginat. Bisby's notes are as follows: "In deciduous woods....
Pileus very small, greenish to yellowish, translucent striate, umbonate;
gills white; stem 1 mm. wide, pale green above, darker green below,
mycelioid at base; spores 12-14 X 5-6 pt; pointed sterile cells at edges
of gills." This collection approaches very closely the classical concept of M. chlorantha. Since the name M. chlorantha has been used
for a species very different from M. citrinomarginata by Ktihner
(see "M. elegans," p. 199), it is doubtful whether the name. should be
continued in use. If we continue to use it, it should be applied to a