Gelidium

a genus of red algae. It includes about 40 species, which are found in warm seas. The thallus is stiff, cartilaginous, often pinnate, and 1-25 cm tall. The sporophytes and gametophytes are similar in structure. Sporophytes yield tetraspores. Gametophytes form carpospores as a result of a sexual process. Gelidium is used for preparing agar-agar, especially in Japan. Gelidium is found in negligible quantities in the USSR in the Sea of Japan and the Black Sea.