peridium

Peridium, pē-rid′i-um, n. the outer coat of a sporophore in angiocarpous fungi.—adj.

A more complicated case is illustrated by Sphaerobolus, where the entire mass of spores, enclosed in its own peridium, is suddenly shot up into the air like a bomb from a mortar by the elastic retroversion of a peculiar layer which, up to the last moment, surrounded the bomb, and then suddenly splits above, turns inside out, and drives the former as a projectile from a gun.

B, Part of vertical section through leaf of Berberis vulgaris, with a, aecidium fruits, p, peridium, and sp, spermogonia.

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

In the last-named genus the peridium is double and the outer layer becomes ruptured and spreads out in the form of star-shaped pieces; the inner layer, however, merely opens at the apex by a small pore.