A Grammatical Dictionary of Botanical Latin

Epigonium,-ii (s.n.II), abl. sg. epigonio: epigonium: “the membranous bag or flask which encloses the spore-case of a Liverwort or Scale-moss when young. Also the nucule of a Chara” (Lindley); (in mosses) "the protective envelope of the developing sporophyte before its rupture into a basal sheath, or vaginula, and an upper calyptra; if persistent [and remaining intact even at maturity] (as in Pyramidula and Bryobartramia), sometimes called a pseudocalyptra," (C&A 1981); “protective envelope of the embryo or young sporophyte, derived primarily from the archegonial venter, in most mosses it ruptures into two parts, a vaginula encircles the seta base and the foot, and the calyptra is carried aloft as a covering on the capsule; i.e. Bryobartramia has a persistent epigonium” (Magill 1990); see ocrea, vaginule.