North American species of Mycena.

34 NORTH AMERICAN SPECIES OF MYCENA

the reaction is recorded. The sections placed in KOH will revive
rapidly, and the details of the spores, cystidia, and basidia can be
obtained as easily as from fresh material. The trama of the pileus
may revive more slowly, but by careful manipulation the details can
be seen very nicely on sections of properly dried specimens. Sections of the stipe can be made as readily as those of the gills and pileus.
In KOH the gelatinous layers have a characteristic translucent or
glassy appearance, and the individual hyphae often appear to be
widely separated. When one is making critical studies it is helpful
to add a drop of a 1 per cent solution of aqueous basic phloxine to the
mount. By the use of this stain small spores become more readily
visible, and the details of the wall can be more clearly discerned.
Occasionally the spores of some smooth-spored species appear rough
under ordinary magnifications of the compound microscope. This is
caused by the accumulation of many small highly refractive oil droplets in a layer next to the spore wall. Because of the relative invisibility of the adjacent smooth spore wall, it then appears as if the oil
droplets were the wall instead, and because of their uneven appearance
the impression of roughness is created. The use of phloxine will
prevent one from being misled.
In order to bring the cystidia, particularly the cheilocystidia,
completely into view (in sections the pedicels and lower portions are
generally obscured by the other cystidia or by the hymenium), it is
often necessary to crush the sections by pressure on the cover glass.
The location of the cystidia should be carefully studied first. The
cystidia shown in the text figures were separated from the hymenium
and from the gill edge by this method. In order to study the details
of the cuticle of the pileus, one should use radial sections (parallel to
instead of across the gills). When these are stained and crushed the
individual hyphae of the cuticle can easily be seen and their details
observed.
The drawings for the text figures were made with the aid of a
camera lucida. The material for the drawings was revived in 2.5
per cent KOH. The cystidia and cells from the gills, pileus, and stipe
are reproduced about 750 times natural size unless otherwise stated
and the spores 1650 times.
CHEMICAL TESTS
The only chemical test applied in this work was the iodine reaction.
A solution of five parts chloral hydrate, two parts water, and an excess