North American species of Mycena.

20 NORTH AMERICAN SPECIES OF MYCENA

length and occur fairly regularly between pairs of complete gills, they
are considered the first or primary row. A second row of still shorter
lamellulae can also be seen in the plates referred to above. It consists
of a very short gill inserted between each primary lamellula and the
adjacent lamella. These are frequently no more than half the length
of the primary lamellula. Thus it can be said that these lamellulae
are in two rows or tiers. The degree to which they develop is likely
to determine whether the gills appear distant or close. In Plate 24
they would be considered close; in Plate 23, subdistant. In this instance, however, part of the difference is caused by the more expanded
condition of the pileus shown in Plate 23. Sometimes when the
second row remains rudimentary and the primary row develops
poorly, the lamellae may appear very distant. This often happens in
M. erubescens. In some species considerable irregularity in the development of lamellulae is encountered, and at times it is even difficult to decide whether or not a single gill reaches the stipe. In
Mycena lamellulae may be entirely lacking or up to three rows may
be present. A knowledge of the variations in their development aids
greatly when one is trying to decide whether the specimen in hand is
characterized by close, subdistant, or distant gills.
The width of the lamellae is usually given as narrow or broad.
This character has some importance, but is best expressed by giving
measurements along with the description. It should always be remembered that a gill 2 mm. wide may be very narrow in a large cap
and quite broad in a small one. It is essentially a relationship of
length to width that one seeks to express. Ventricose gills (those
abruptly widened in the middle) are rare in Mycena.
In some North Temperate species there is a strong tendency to
develop veins in the spaces between the gills. It is most noticeable
in those related to M. galericulata and also in M. pura. So far as
these species are concerned, it does not appear to be an important
character, but in the tropics the situation appears to be different.
Van Overeem (1923-26) has described and illustrated some tropical
forms with poroid hymenia but otherwise apparently related to
M. pura.
FLESH
Certain haracteristics of the flesh of the carpophore are important
taxonomically. The odor and taste are among the foremost of these.
M. cinerella has a very characteristic rancid taste. In most, however,