ca·lyp·tra 
(kə-lĭptrə)
(kə-lĭptrə)n.
1. The protective cap or hood covering the spore case of a moss or related plant.
2. A similar hoodlike or caplike structure, such as a root cap.
[Medieval Latin, from Greek kaluptra, veil, from kaluptein, to cover; see kel-1 in the Appendix of Indo-European roots.]
ca·lyptrate′ (-trāt′) adj.