ngly calcareous, cinereous-white;
stipe variable, generally tapering upward, always distinctly deeply
plicate-furrowed throughout, in color dark, opaque, sometimes touched
with white or gray; capillitium abundant, the white lime-knots, varying
in size and shape, connected by rather long hyaline threads, with here
and there an empty node; spore-mass black, by transmitted light, dark,
sooty brown, minutely papillose, 10-11.5 mu.

This remarkable species, while not at all difficult of recognition to
one familiar with its phases, is withal very difficult to define.
Normally stipitate, it often shows from the same plasmodium all sorts of
forms, the shape of the fructification dependent apparently upon
external conditions prevalent at the time. The amount of calcium also
varies, especially in the capillitium, where there is usually much, with
a tendency to the formation of something like a pseudo-columella; the
outer net in such cases nearly destitute. The calcium in the stipe also
varies; the black or brown stipes are, of course, free from it; the gray
or white, calcareous.

In this large and difficult genus, since spore-color is receiving
increased consideration,--see No. 31 preceding,--it is proper to note
that in the present case two types appear, one with spore-color under
the lens, as described, the other with spores violaceous with no trace
of black; unshadowed.

The preceding description is based on material assembled during forty
years. The form is easily discoverable by any collector throughout the
entire valley of the Mississippi and eastward to Nova Scotia. For its
naming, students in America have vainly waited the decision of those
having access to mycologic types in Europe. It seems now certain that
the species is extremely rare in the old world if there occurrent; never
seen by any of the earlier taxonomists including Fries and Rostafinski;
perhaps adventitious in these later years, although thus far no specimen
from Europe has reached this table.[24] _P. nefroideum_ of Strasburg
herbarium turns out, after all, _teste_ Lister, to be _P. compressum_
Alb. & Schw., which accordingly shall now enjoy state and station of
its own; our concern in European nomenclature, in the present instance,
almost disappears, and we return to our synonymy from this side of the
sea.

Mr. Lister would recur to Dr. Peck's _Didymium connatum_, which indeed
represents the present species. In such disposition, how gladly would
all