Peridium

Part of speech: noun

Definitions

1. The outer protective covering that encloses the spore-bearing structure of some fungi or slime molds
2. A layer that surrounds and shields the reproductive part of specific fungi or molds from external damage
3. An enclosing coat forming the exterior of certain fungal or slime mold fruiting bodies to protect spores

Etymology: Ancient Greek writers used "pēridion" for a small pouch or purse, a humble everyday object that gave no hint of the mycology to come. The word was taken up in New Latin, the international scholarly Latin of early modern science, and naturalists applied it to the enclosing covering of certain fungi and slime molds. The image is simple: the spores sit inside a little bag, much as coins might be kept in a purse. The choice of name follows a common pattern in scientific naming, where scholars reached back to classical vocabulary to label newly observed structures. Here the Greek diminutive ending gives the sense of "little" container, so the term describes the protective wrapper itself rather than the spores within it.