Flora. The capillitium is figured
by McBride in The Myxomycetes of Iowa. This is the only form I have met
with in this country.

III. DIDERMA, Pers. Sporangia subglobose and stipitate or more often
sessile, sometimes plasmodiocarp; the wall a thin membrane, with an
outer layer composed of minute roundish granules of lime, which are
usually compacted into a smooth continuous crust. Stipe present or
mostly absent; the columella usually well developed. Capillitium of very
slender threads, stretching from the columella to the wall of the
sporangium, more or less branched, and combined into a loose net by
short lateral branchlets. Spores globose, violaceous.

This genus is easily recognized by the smooth crustaceous layer of lime
on the outer surface of the sporangium; in many cases this easily shells
off or breaks away. Such a coating occurs in a few species of Physarum,
but here the vesicles of lime attached to the threads distinguish them.
This is Chondrioderma of Rostafinski's monograph; the reason for coining
a new name and entirely discarding the old one is not apparent.

Sec.1. LEANGIUM. Sporangium usually stipitate; the wall at maturity
separating from the inner mass of spores and capillitium and splitting
in a stellate manner, the segments becoming reflexed.

1. DIDERMA RADIATUM, Linn. Sporangium depressed-globose, the base
flattened or umbilicate, stipitate or nearly sessile; the wall smooth,
whitish or pale brown, splitting from the apex downward into a few
reflexed irregular segments. Stipe short, thick, erect, tapering
downward, standing on a thin membranaceous hypothallus; the columella
large, convex, globose or obovoid, roughened. Capillitium of slender
dark-colored threads, radiating from the columella, simple or branching
outwardly. Spores globose, minutely warted, dark violaceous, 8-10 mic.
in diameter.

Growing on old bark and wood. Sporangium .8-1.2 mm. in diameter, the
stipe shorter than the diameter, sometimes nearly obsolete. Apparently
rare in this country.

2. DIDERMA FLORIFORME, Bull. Sporangium globose or obovoid, stipitate,
growing closely crowded together on a thin brown membranaceous
hypothallus; the wall smooth, varying in color from whitish or yellowish
to bright brown, splitting into irregular segments, which become
reflexed and revolute. Stipe long, erect, white or yellowish to brown;
the columella elongated, obovoid to clavate, roughened, colored as the
stipe. Capillitium of dark-c