Cystoseira

Cystoseira is a brown alga in the order Fucales.

Description
Cystoseira is characterized by highly differentiated basal and apical regions and presence of catenate pneumatocysts (air-vesicles). In Cystoseira old plants have an elongated main axis, and in time the primary laterals become proportionally elongated. Their lower parts are strongly flattened into ‘foliar expansions’ or basal leaves. Fertile regions which bear conceptacles are known as receptacles. These are normally found at the tips of the branches. Their basal and apical regions are highly differentiated. They posses catenate pnuematocysts (air vesicles). The aerocyst or air vesicles keep the organism erect, by causing it to float in strong currents.

Distribution
Cystoseira is one of the most widely distributed genera of the Fucales order and provides an essential habitat for many epiphytes, invertebrates, and fish. Cystoseira is found mostly in temperate regions of the Northern Hemisphere, such as the Mediterranean, Indian, and Pacific Oceans.