North American species of Mycena.

14 NORTH AMERICAN SPECIES OF MYCENA

SIZE AND STATURE OF CARPOPHORES
Size and stature are so likely to be influenced by local conditions
that one must allow for considerable variation in both. In the following taxonomic treatment both have been used to some extent to
characterize species, but only after careful study. Although Mycenae are small fungi, there is a surprising range of variation in both
size and stature. Despite the use here of size as a means of separating
the diminutive species from the others of the subgenus Eumycena,
its limitations are clearly realized. It does not appear advisable to
erect new taxonomic units other than forms with size alone as the
major distinction, but as a character of general value in distinguishing
a troublesome group of species comprised of several phylogenetic
lines, size serves a very useful purpose.
Certain species of Mycena are variable in stature, the variations
apparently being caused by local factors which frequently dominate
a habitat. M. erubescens, for instance, may be short and squatty if
it grows in the open on bare soil, or it may develop a greatly elongated
stipe when growing alongside logs where there is an accumulation of
old leaves with high moisture content. Under certain conditions
M. pura may have a cap barely 1 cm. broad, and under others a cap
5-6 cm. broad, with all other parts in proportion. In the descriptions
the usual range in size has been given, and the variations from it have
been indicated in parentheses. The smallest species of the Deminutivae have pilei approximately 1 mm. broad, whereas the largest species
of the Typicae have caps up to 7 cm. If one seeks for the most
accurate gauge for measuring stature, he will find it in the diameter
of the stipe. Even the smallest and slenderest carpophores of typically robust species will have thicker stipes than those which belong
to the minute Mycenae, although the pilei may be exactly the same
in both size and shape. Atkinson and Kauffman recognized thickness
of the stipe as the least variable of all the parts concerned, and my
field studies have verified their observations. One word of caution
should be added: Be careful to take the measurements from fully
matured specimens. The stems, particularly among the lignicolous
species, are often rather thick in the immature carpophores, but become thinner as they elongate and the pileus expands.
COLOR
One cannot help being impressed by the diversity of color exhibited by the various members of the genus, and as a character it is