Sphagnum rubellum

The sporangium. It has no teeth. When it was immature, an operculum covered the top. As the sporangium matures, pressure builds inside, eventually reaching 3 -5 Atmospheres. When the pressure is too great, the operculum pops off and the spores are dispersed, shot out like bullets from a gun. Sphagnum spores are dispersed all at once, not over a long time as they are in most mosses.