As presently defined, Cystoseira comprises fucoids characterised by antherozoids without stigmata, few antheridial branches, trichothallic hairs in conceptacles, large ovoid oospheres, and eggs that remain attached to the surface of the receptacles through mucilaginous stalks until after fertilization.

Species from the Indian and Pacific oceans are presently included in different genera.

[2] Cystoseira are important habitat-forming species in coastal waters of the Mediterranean and Northeast Atlantic.

They require good water quality, and can be used as bioindicators for pollution levels.

[4][2][5] As a result, most species were moved to the genera Stephanocystis, Polycladia, Sirophysalis, Gongolaria and Ericaria.