This is the tissue of the old gametophyte neckthat persists on the top of a moss spore capsule.!-- google_ad_client = "pub-6700624969687881"; google_ad_width = 234; google_ad_height = 60; google_ad_format = "234x60_as"; google_ad_type = "text"; google_ad_channel ="7512561969"; google_color_border = "FFFFFF"; google_color_bg = "FFFFFF"; google_color_link = "448079"; google_color_url = "448079"; google_color_text = "414141";
in mosses, a derivative of the distal archegonium forms a hard, protective layer around the developing sporophyte called the epigonium. Later the epigonium breaks up, but the sporophyte retains a conical "dunce cap" over its distal end, and sometimes a ring around the base. The cap is the calyptra. The piece retained around the base is the vaginula.
the hood or cap covering the calyx of certain plants: e.g., the California poppy
Hood or cap-like part covering the calyx of certain plants.
in mosses, a cap-like structure covering or partly covering the capsule and derived from the neck of the archegonium; in a flower (= operculum), a cap formed by fusion or cohesion of perianth parts and covering the stamens and carpels in the bud.
A lid or hood. In mosses, the thin veil or hood covering the mouth of the capsule.
enlarged archegonium that surrounds embryo
In bryophytes (especially mosses), the calyptra is a cap of gametophyte tissue that protects the sporangium. This cap is lost when the sporangium capsule is mature and ready to release the spores. In flowering plants, the calyptra is a covering tissue for stamens and carpels.