Calyptra is a small sheath of cells, derived from the archegonia, which covers the top of the capsule. Capsule is a sporophyte generation of mosses. Antheridia is a small structure that produces sperm in bryophytes or pteridophytes. In fungi, the young sporangium is a white spherical structure situated at the free and the sporangiophore. At maturity, it turns black. The black colour is due to the presence of sooty spores within. In the centre of the sporangium is a large dome-shaped structure called the columella.