About Plocamium cartilagineum (L.) P.S.Dixon
Plocamium cartilagineum is an erect red alga that grows up to 10 centimeters long. Its main axis is flattened, with regular flattened branches growing from both sides. Branches alternate between long and short: short branches on one side of the axis lie opposite longer branches on the other side. These longer branches bear two or three short, curved branches arranged in a series in a comb-like pattern. The entire thallus is corticated. This species' branching pattern is similar to the other European Plocamium species, Plocamium lyngyanum and Plocamium maggsiae, which were only distinguished from each other and this species recently. This alga is common growing on rock in the lower littoral zone, and in deeper water down to 30 meters. It is common throughout the British Isles, including Shetland and the Channel Islands. Its overall distribution ranges from the Faeroes and Norway south to Senegal, and also includes the Mediterranean and the Canary Isles. This species is dioecious. Male reproductive structures are microscopic. Spermatangia are held in sori on the youngest branches. Female cystocarps grow up to 1 millimeter in diameter and form on the margins of the fronds. Tetrasporangia are microscopic.
