These capsules are closed at the summit by a cap, forming an operculum, so that they sometimes appear as if formed of two valves.
"The Mechanism of Life"
Stéphane Leduc
Sporangium usually minute, broadly funnel-shaped, stipitate; operculum always more or less convex, rarely approaching a hemispherical shape, dehiscent in a regular circumscissile manner.
"The Myxomycetes of the Miami Valley, Ohio"
A. P. Morgan
The wall a thick, brownish membrane, externally smooth and variously colored, sometimes uniformly light or dark umber, sometimes dark brown below and brownish white above; the operculum brownish white, darkest in the center.
"The Myxomycetes of the Miami Valley, Ohio"
A. P. Morgan