Cookeina is a genus of cup fungi in the family Sarcoscyphaceae, members of which may be found in tropical and subtropical regions of the world. Species may be found on fallen branches of angiosperms, trunks, and sometimes on fruits. The Temuans of Peninsular Malaysia are reported to use certain species from this genus as food, and also as a bait for fishing, where it is rubbed against the hook.
When mature apothecia become filled with water, the asci absorb some of that water and develop a Turgor pressure, a hydrostatic pressure within the ascus which put pressure on the tip of the ascus, held in place by the rigid ascus wall. As the water level in the cup reduces due to evaporation, the asci tips dry out, resulting in a negative vapor pressure that ultimately results in the thin tissue at the wall of the apex (the operculum) breaking outward, releasing the spores.