North American species of Mycena.

26 NORTH AMERICAN SPECIES OF MYCENA

or even from the cells of the hypoderm if the pellicle is not well developed. These processes are comparable to the rodlike projections
found on many of the pleurocystidia and cheilocystidia. In this
classification setae are regarded as cystidia. They are usually long,
pointed, thick-walled structures, and in Mycena occur chiefly as pilocystidia or caulocystidia. In Marasmius cohaerens, an agaric which
in the past was often placed in Mycena, they occur as pleurocystidia
and are characterized by dark-brown thickened walls. A glance
through the text figures will illustrate the great diversity in form and
markings that the cystidia of Mycena exhibit.
The simplest cystidia are the smooth clavate to cylindric type
present in M. cineraria and M. arenaria. These can ordinarily be
distinguished from immature basidia only by their greater size.
Another simple type is found in M. amicta and M. subcaerulea, in
which the cheilocystidia are filamentous, giving the impression that
they are merely outgrowths of the hyphae of the gill trama and not
otherwise differentiated. In M. speirea they are at first hardly distinguishable from young basidia, but as they mature they elongate
greatly and become more or less filamentous. In a large number of
species the cystidia are fusoid-ventricose and smooth, but the apex
may be pointed, obtuse, or forked. Sometimes two or, more long
fingerlike protuberances develop from the upper part of the enlarged
portion. The term "fusoid-ventricose" is here applied to any cystidium which has the midportion distinctly enlarged and which tapers
to the apex as well as to the pedicel. There are all degrees of variation
between this and the clavate type, and frequently one finds many of
the variations on different parts of the same gill progressively from the
stipe to the margin of the cap. The same variation can be found if one
compares the lamellulae with the complete gills. Some species have
cystidia in which the widest portion is near the apex andithe tip is
greatly reduced in size, forming only a small protuberance. Such
cystidia are described as "mucronate." In M. pectinata the majority
of the cheilocystidia are of this shape. The mucronate cystidia may,
like the fusoid-ventricose individuals, give rise to fingerlike projections
over the apex, as is shown in the text figures. In some species the
cystidia remain more or less clavate and develop numerous fingerlike
prolongations on or near the apex, and in others these projections
may become variously branched or contorted. As the number of
projections on the clavate cystidium increases, they tend to become
smaller, and finally one arrives at the clavate-echinulate or verrucose