Species:

Note: The species is filamentous and finely branched, and together with Ectocarpus it may be very common in the upper sublittoral in spring and summer. It is uniseriate but may have occasional cells with longitudinal divisions. It has irregular or opposite branching. It can easily be identified when it is fertile, by having intercalary reproductive cells (unilocular or prlurilocular zoidangia) placed in a row between vegetative cells.