The North American species of Psathyrella.

1972]

PSATHYRELLA

11

long ago that, typically, spores from 4-spored basidia in a given species are smaller
than those from basidia bearing only two spores. In measuring spores, if possible,
use material from a deposit. If the latter are not available, and crush-mounts or
sections of the hymenophore are to be used, be sure to measure the most deeply
colored individuals. In such mounts it is not at all uncommon to find many pale
colored spores often of various sizes, and in some mounts these may be of various
shapes, such as being much longer and narrower than the majority. I have found
the spores from deposits to be much more constant in shape and pigmentation than
those from pieces of the hymenophore, and suggest that the "abnormal" spores are
often not discharged.
The color of the spore deposit is a feature of some value taxonomically, but
I have not used it here as a major character. First, the color ranges from brick
red through cocoa-brown to various shades of chocolate-color to black. One should
note the color of the spores from air-dried deposits. It is a simple matter to place
the spore deposit on a layer of silica gel (activated), cover the dish and allow to
stand for 15 minutes, by which time desiccation is reasonably complete. In the
North American species one finds sterile or partly sterile specimens frequently
enough to cause some concern about using the color of the deposit taxonomically.
Spores from partly sterile specimens are often paler than normal for the species,
and of course one is almost certain to get a thinner deposit-if a deposit is obtained.
The color of the spore under the microscope as mounted in KOH and also as
mounted in Melzer's is very useful. In KOH spores of many species are cocoacolor at first but soon darken to dark chocolate color or chocolate-brown (which
is a paler shade). In those species in which the deposit is pink to brick red, the
spores under the microscope often appear hyaline or nearly so. However, in a
number of species in which the spore deposit is avellaneous to wood brown, the
spores under the microscope may be a dingy ochraceous-hyaline or a tinge of
vinaceous may be added, as in P. spadicea. At the other end of the color spectrum
we have the species which give an essentially black to dark chocolate colored
deposit. Under the microscope these spores may be opaque and practically black,
or they may be black with an obscure ochraceous undertone (the latter are here
described as fuscous-the term not being used in the sense of Ridgway). The term
dark chocolate color indicates the presence of a slight violaceous tint and is close
to "fuscous"of Ridgway. Chocolate-brown indicates a cinnamon undertone and is
most often observed on spores which when first mounted in KOH were cocoacolored. The latter term is to be interpreted literally-the color of powdered
cocoa. Bister is used approximately in the sense of Ridgway but is also expressed
by the term medium date brown, a dark date brown being near that of the color
plate "mummy brown" of Ridgway. The light source for the microscope is an
important factor in observing color under the microscope. All observations in the
following taxonomic treatment were made with a Leitz Ortholux microscope with
their standard incandescent bulb (Osram 8110, 6V, 5A). A white ground glass
filter was used. The high power oil immersion used was an apochromat NA.
1.4 lens, and the low-power oil a Fluorite 54 x, NA 0.95 lens. No adjustment can
be made for individual differences of color perception each person must arrive
at his own evaluation of this factor, but the terms used in the taxonomic treatment indicate such broad color groups that there should be little trouble in
evaluating the terms relative to the spores under observation.
Certain changes occur in the color of spores when revived in KOH or mounted
in this medium when fresh: by far the majority of species have spores which,
when first mounted in KOH for the first few minutes are cocoa-colored, chocolate