peridium

It is never crowded, shows no plasmodiocarpous tendencies, while the outer peridium is generally deciduous except at the base and falls in flakes.

From The North American Slime-Moulds A Descriptive List of All Species of Myxomycetes Hitherto Reported from the Continent of North America, with Notes on Some Extra-Limital Species by Thomas H. (Thomas Huston) MacBride

Sporangia gregarious, clustered but distinct, sessile small, about .75 mm., bright yellow, peridium double.

From The North American Slime-Moulds A Descriptive List of All Species of Myxomycetes Hitherto Reported from the Continent of North America, with Notes on Some Extra-Limital Species by Thomas H. (Thomas Huston) MacBride

Inner peridium distinct from the outer all round; capillitium nearly free, collapsing when mature, threads long and brittle; spores dingy olive, turning brown; base stem-like, broad and blunt, with root, obconical, somewhat spongy.

From Student's Hand-book of Mushrooms of America, Edible and Poisonous by Thomas Taylor

The author hesitated about the generic reference, finally referring it to Diachaea despite the lack of calcium, because it was sessile and had a peridium rather more persistent than is usual in comatrichas.

From The North American Slime-Moulds A Descriptive List of All Species of Myxomycetes Hitherto Reported from the Continent of North America, with Notes on Some Extra-Limital Species by Thomas H. (Thomas Huston) MacBride

When the spores are ready for dissemination a small aperture appears in the top of the peridium, through which they push their way outwards like a little puff of smoke.

From Student's Hand-book of Mushrooms of America, Edible and Poisonous by Thomas Taylor