peridium

Chiefly on moss, the pale ashen sporangia generally very small, mounted on the tips of the leaves, sometimes sessile, sometimes with a distinct black stipe in which case the peridium is distinctly umbilicate.

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

This species resembles B. capsulifera, but is distinguished by a more strongly rugulose less calcareous peridium and a more profuse development of filamentous stipes, but especially by the character of the spores.

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

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

In some instances the peridium is almost smooth, and sometimes cracks in areas, inner peridium thin and tough.

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