Bladderwrack

Bladder-wrack, the popular name for those olive-brown algae of the genus Fucus, which have air-bladders or floats hollowed out in the tissue of their frond-like thallus. Fucus vesiculosus, with a midrib and its bladders in pairs on each side of it, and F. nodosus, with a narrow thallus, no midrib, and bladders arranged singly, are the commonest sea-weeds on our coasts, where they were formerly collected as kelp, and are still used for manure and for iodine baths.