The North American species of Psathyrella.

1972]

PSATHYRELLA

25

represent one of the most poorly explored groups in the plant kingdom. It must
be kept in mind that fleshy fungi are an important world source of food (Singer
1961), and on this basis alone, intensive study of the group is justified.
RELATIONSHIPS TO OTHER GENERA
In my estimation it is logical to seek for the ancestral types of the Coprinaceae
in more primitive rather than in other highly evolved groups. Hence, though
spores of Leucoagaricus and some other Lepiota-like genera have a germ pore,
I am not inclined to relate to them the family Coprinaceae. To me it is more
logical to look back through the Bolbitiaceae to Galerina as a primitive group.
If one simply compares characters, it is at once evident that the Bolbitiaceae
are anatomically very similar to the Coprinaceae, and it is tempting to visualize
the latter as having arisen from the former through mutations in pigmentation
of the spore. That such changes can occur has been demonstrated from material
collected in nature, the subgenus Conocybella for example. The spores of the
type species were fuscous in deposit when fresh, but after standing in the
herbarium over the years they now have almost the same pigmentation as
some Conocybe spores but duller. It has long been known that Agrocybe of the
Bolbitiaceae has some species which give an earth-brown deposit that for all
practical purposes is the same color as some spore prints of Psathyrella. Agrocybe
dura, for instance, is often mistaken for a Stropharia. Smith and Hesler (1969)
discussed the intergrading color of spore deposits between Pholiota and the
strophariaceous genera. In short there is ample evidence that purple-brown
spored agarics could have arisen from those featuring rusty brown spores,
particularly in groups where a germ pore is involved.
The problem of related genera in the Coprinaceae is simple and straightforward. Pseudocoprinus is a genus recognized by some authors and is distinguished from Psathyrella by two features; namely the presence of brachybasidioles in the hymenium and a plicate striate pileus. Both of these features
are found in Psathyrella but not in combination (by definition). The distinction
may be regarded as artificial by some, but it must be kept in mind that there
is a smooth progression through Psathyrella to Coprinus in the evolution of
physiological and morphological features. The problem resolves itself into
whether the family should contain a single genus or be divided. The latter
conclusion is the one accepted here and Pseudocoprinus is recognized on that
basis. It represents a major step in the evolution of the Coprinus-type basidiocarp
from the Psathyrella-type. The genus differs from Coprinus in that the process
of autodigestion has not been developed.
Coprinus, featuring the process of systematic autodigestion of the hymenophore after spore liberation, is, without question, the most highly specialized
genus in the family; but its recognition is based mainly on a physiological process.
Morphologically speaking, its other characters can all be traced to primitive states
in Psathyrella.
Panaeolus is a "satellite" genus closely related to Psathyrella, but differing
in the stability of the spore pigment and spore wall in concentrated sulphuric
acid and in having mottled gills as the spores mature. It connects to Psathyrella
through the subgenus Panaeolina of the latter (as recognized here). The question
as to whether Panaeolina is a valid genus or belongs in Panaeolus or Psathyrella
is an open question at present. My disposition of it is based on its Psathyrellaaspect and, in view of the diversity in Psathyrella, its generic features seem