(pl. caveae, adj. caveate) ( Skvarla and Larson, 1965) A cavity between two layers of the exine extending to the colpus margin where the layers meet. Example: Ambrosia (Compositae). Caverna (pl. cavernae) ( Thomson and Pflug, 1953) Synonym of fastigium. Comment: Originally a distinction was made between a separation of two layers of the ectexine, which was called a praecaverna, and a separation within the endexine, a postcaverna. The term is not used to describe recent pollen grains. Cavium ( Thomson and Pflug, 1953) A subpolar chamber formed at the end of three anastomosing cavernae. Cavum (pl. cava, adj. cavate) ( Fægri and Iversen, 1989) Synonym of cavea. Cavus (sensu Skvarla and Turner, 1966) Synonym of cavea. Centrosymmetrical (adj.) ( Straka, 1964) Synonym of radially symmetric.