Mannitol is a complex carbohydrate functioning as stored food in Phaeophyceae (Brown Algae). Fucus is a brown alga. In contrast, Porphyra and Gracillaria belong to Rhodophyceae (Red Algae), which store food as Floridean starch, while Chara belongs to Chlorophyceae (Green Algae), which stores food as starch , .