The North American species of Psathyrella.

1972]

PSATHYRELLA

21

near the septa and their behavior in KOH, and the color of the wall (brown)
of the cuticular cells of some species when revived in KOH.
The degree of differentiation of a laticiferous system, the arrangement of
the hyphae of the hymenophoral trama (within the genus), and the arrangement
of the hyphae in the context of the pileus appear quite homogeneous for the
genus as a whole. Clamp connections are present in all but a few species (in
which the material available to date has not been abundant). In view of what
has been found in Suillus (Boletaceae) by Pantidou (1961) and others, one can
expect to find an occasional clamp in the "clampless" Psathyrella species. Hyphal
disarticulation especially in relation to hyphae of the veils needs further study
as do the veil hyphae generally-but from fresh material. On most dried specimens of Psathyrella in herbaria generally one cannot get a good sample of veil
hyphae. It is the author's intention, now that this work has been brought to
a reasonable stage of completion, to study the features of the veil in relation
to species concepts as here proposed. It is true that the veil furnishes important
characters in the taxonomy of Coprinus.
SUBSTRATE RELATIONSHIPS AND ECOLOGY OF SPECIES OF PSATHYRELLA
The substrate relationships for most species appear to be rather monotonousmost occur on wood in various stages of decay or on the dead remains of both
monocots and dicots, such as piles of leaves, compost piles, accumulations of
herbaceous stems, etc. Some species clearly cause a primary decay, but most
probably attack wood already partly decomposed. It is common to find Psathyrella on logs so rotten that they are ready to crumble or have crumbled into
a shapeless mass. Very little is known of the basic nutrient requirements for
the various species-in fact our inability to identify species accurately has
probably held up or rendered questionable to date studies on their biology.
However, most species can be readily obtained in culture, and it is hoped that the
present study will aid in furnishing a serviceable foundation for critical investigations of the species in the laboratory. One phase which is of interest is the
possible interdependence of these fungi on the byproducts of decay as produced
by such fungi as Mycena leaiana and Xeromphalina tenuipes.
Although most Psathyrellae have substrate relationships rather broad in
scope, some are highly specialized. Psathyrella epimyces, for instance, is parasitic
on Coprinus comatus, and, at least in my own front yard, has apparently killed
flourishing mycelium of the latter. Psathyrella arenulina and P. ammophila are
associated with dune grass-either living on the dead roots, etc., or possibly
forming mycorrhiza with the grass. As will be noted in the keys, a few species
occur on Sphagnum. Psathyrella typhae is found most frequently on dead culms
and leaves of Typha-usually fruiting just above the waterline. Some Psathyrellae prefer grass land, but it is not known if they attack the roots of the grass
or live on dead material-one would guess the latter. A number are coprophilous,
as are so many species of Coprinus. From a gardener's standpoint such species
as P. candolleana might well be investigated for their ability to compost coarse
lignicolous debris such as herbaceous stems, piles of leaves, etc.
When compared with other genera, Psathyrella would, by necessity of the
number of species involved, be regarded as one of the major "clean-up" genera
of the Agaricales along with Coprinus and Pholiota.
The seasonal fruiting habits of Psathyrella species are much like those of
the above mentioned genera. Some fruit in the spring, some in the summer and