An operculum or (in plural) opercula are botanical terms describing a certain structure or structures of certain vascular plants, mosses, or fungi which act as a cap, flap, or lid. In vascular plants, an operculum may also be called a bud cap.
Examples of structures identified as opercula include:A flap of the sporangium of a moss, covering the peristome (appendages surrounding the mouth of a moss capsule).
The cap of the ascus in certain ascomycetous fungi.
A lid covering the aperture of pollen grains.
The bud cap covering the flowers of Eucalyptus and Corymbia trees which falls off as they open.
The covering of a pyxidium (fruit capsule whose upper part falls off when the seeds are released) of a plant, such as the plantain.
The flared leaflet that prevents a pitcher plant from accumulating rainwater.