AbstractExistence of D‐galactose and 3,6‐anhydro‐L‐galactose in the polysaccharide obtained from Pterocladia tenuis was confirmed. The polysaccharide extracted from Bangia fusco‐purpurea was fonud to consist of DL‐galactose, 3,6‐anhydro‐L‐galactose and 6‐0‐methyl‐D‐galactose. Results of studies on these polysaccharides with methods of periodic oxidation or partial hydrolysis were reported with the suggestion that the main part of the polysaccharides extracted from pterocladia tenuis Okam might be built up from a repeating unit