What is "cystocarp"

Cystocarp \Cys"to*carp\ (s?s"t?-k?rp), n. [Gr. ???? bladder + karpo`s fruit.] (Bot.) A minute vesicle in a red seaweed, which contains the reproductive spores.

n. A minute vesicle in some seaweeds, containing the reproductive spores.

A cystocarp is the fruiting structure produced in the red algae after fertilization, especially such a structure having a special protective envelope (as in Polysiphonia).