calyptra

noun4

1. •
   In bryophytes, a thin hood of tissue that forms from the archegonium and covers the developing sporophyte and is shed as it ripens.

   • (b) sporophyte with foot reduced, the entire sporophyte enveloped by the calyptra, which is ± stipitate at the base. — 1992
2. •
   any cap-like covering of a flower or fruit, such as the operculum over the unopened buds of Eucalyptus flowers
3. •
   Any of various coverings at the tips of structures, in the terminology of various authors; for example rootcaps and the apical cells of trichomes.
4. •
   In flies such as the housefly, Musca, in the taxonomic order Diptera, zoological section Schizophora, subsection Calyptrata, the calyptra is a membranous rearward extension of the forewing; it covers the haltere.