North American species of Mycena.

18 NORTH AMERICAN SPECIES OF MYCENA

others the pileus may appear pubescent because of projecting hairs of
almost microscopic size. One, M. stylobates, has coarse projections
made up of fascicles of hyphae.
The surface of the stipe exhibits the same variations in its characters as the pileus. It may be scurfy or pruinose owing to minute
hairs or cystidia, glabrous and polished, or viscid. In some, such as
M. polygramma, it may be appressed-fibrillose and develop distinct
longitudinal striations or lines. The base may be naked or covered
with strigose mycelial hairs. In one group the stipe is characterized
by an abrupt basal disc or bulb, a character of major importance.
In many small species it is perfectly glabrous at the base and is inserted abruptly onto the substratum. This type of attachment is
significant. In most species the base of the stipe is somewhat strigose.
The degree to which this development takes place depends almost
entirely on local conditions. If a cluster of carpophores arises from
a hard exposed surface, the stipes may be inserted directly on the
substratum, with few hairs present. If the cluster arises from deep
in the rotten wood, the buried portion will more than likely be conspicuously strigose.
The base of the stipe may be characterized by a long rootlike
projection, termed "pseudorhiza" by Fayod (1889). This is typical
of a number of species, such as M. galericulata, M. megaspora, M.
nodulosa, and M. Kauffmanii. Buller (1934) has discussed this
structure in detail, so that the following comments will be limited to
its use as a taxonomic character. It is important, but certain species
in which it is characteristically present may not show it if the fruiting
bodies originate from a hard surface instead of coming from deep in
the ground or from other substrata. In addition, the unobserving
collector may fail to obtain it. The pseudorhiza is broadest at the
point where it reaches the surface, and it tapers from there downward
to a slender rootlike strand which, if one follows it, is found to be
attached to an old root or some other piece of buried wood. Occasionally more than one fruiting body may develop from a single
pseudorhiza, as is shown in M. megaspora (Plate 61). In Mycena
this variation appears to be rare. Many species related to M.
galericulata and M. megaspora have a tendency to develop a long,
somewhat rooting, strigose base. M. semivestipes and M. laevigata
are typical examples. This type of base cannot be classified as a
pseudorhiza.