The North American species of Psathyrella.

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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

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brown or blackish. Cocoa-colored spores typically darken in 15 minutes to
grayer shades or to violaceous-browns (many change to dark chocolate color).
However, in some, if allowed to stand for a half hour or more the color finally
fades to nearly hyaline. This happens sooner for some species than others, but
the difference has not been used here taxonomically since it hardly seems practical
and its significance is open to question. At present we do not know as much as
we should as to how many of the dried specimens have been treated in the past,
or what effect age of the spores has on the reaction. It was also noted that for
spores initially pale colored to hyaline in KOH that these usually became
clouded grayish to pinkish-gray (avellaneous) on standing for 15 minutes or
longer. This change is not regarded here as important in distinguishing species,
but is very important as an aid to placing to genus or family dried specimens
sent in for identification. The members of the Bolbitiaceae have spores not
showing this feature. As will be seen again under the discussion of color changes
in tramal hyphae in KOH, the latter mounting medium produces some color
changes of taxonomic significance but there are limits to their practical application, and a changing pattern of pigmentation in the medium seems almost to be
the rule rather than the exception.
The use of Melzer's reagent on spores is of some value taxonomically, but it
developed during the course of the study that its taxonomic use had definite
limitations. The medium does enable one to measure the thickness of the spore
wall more accurately than does KOH because of the sharp definition. In KOH
mounts it has been demonstrated that at least for some species the wall swells
more than in Melzer's and is less sharply defined. As to the color reaction in
Melzer's, we find dark spores (blackish to dark date brown or dark chocolate
colored spores) to be bay-red to bay-brown generally, but in by far the majority
of species the spores are tawny-red to reddish tawny, and in those with pale
spores, the color in Melzer's ranges from near "ochraceous-tawny" (yellowbrown) to pale ochraceous to nearly hyaline (very rarely). Also, one can
generally predict the color in Melzer's from viewing the color intensity in KOH.
One of the disappointing features of the present investigation was that no
amyloid reactions were found either in spore walls or in spore content, as has
been found in the boleti for instance. However, I did not bleach spores of a
significant number of species to test them after the pigment had been destroyed.
It has been stated in the literature that the spores of Psathyrella discolor in
concentrated H2SO4 and that this feature is a generic difference between Psathyrella and Panaeolus, for instance (Singer, 1951). Preliminary tests were made
on the spores of nearly all the species in the present work, and a pattern of
behavior was found which is of some interest. It was found, as others have
found, that, generally speaking, a violet to slate-violet tone develops in most
species before the spores disintegrate in the mounting medium. To this extent
one can use the feature as an aid in identifying the genus, but since for 395 out
of a possible 400 species this can be done more easily by other means, its practical
value as a taxonomic tool is questionable. However, it does seem to have value
in the Coprinaceae in tracing the evolution of some groups of species, and so its
systematic value should not be abandoned.
The interesting point worth mentioning here, is that, as for KOH, there is
considerable diversity in the color reaction within the genus. The common
reaction is to dull lilaceous or slate-violet followed by rupture of the spore and
disintegration of the wall in 10 minutes or more. Psathyrella alluviana is an
example. In P. elwhaensis they became Corinthian purple (very bright) but