peridium

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 calcareous deposit on the peridium is usually very rich and under a lens appears made up of countless snowy or creamy 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

In habit it is very much like some forms of P. sinuosum but differs in the depressed, rather than compressed sporangia, and in the brown color of the outer peridium.

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 to which the peridium still adheres, although in 3 c in shreds.

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

The fruit-bodies are of very various shapes, showing a differentiation into an outer peridium and an inner spore-bearing mass, the gleba.

From Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" by Various