Peridium

The outer layer of this bird's nest fungus (Crucibulum laeve) is the peridium.
Internal surface of the peridium of the rare myxomycete Tubifera dudkae is covered with folds

The peridium is the protective layer that encloses a mass of spores in fungi.[1] This outer covering is a distinctive feature of gasteroid fungi.

  1. ^ British Fungus – Flora, by George Massee; page 6; Published by George Bell and Sons, 1892