calyptra

Noun

calyptra (plural calyptras or calyptrae)

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, Rudolf M[athias] Schuster, The Hepaticae and Anthocerotae of North America: East of the Hundredth Meridian, volume V, Chicago, Ill.: Field Museum of Natural History, →ISBN, page 4
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.