Any of a large group of complex heterogeneous polysaccharides present in many plants and algae. They occur in the root, bark, seeds, and other parts. Various functions have been proposed, including food reserve, water absorption and storage, and aiding seed dispersal and germination. Mucilages are hard when dry and slimy when wet. Unlike gums, mucilages are not found on the plant surface as exudates following injury or attack by pathogens. They are a form of soluble fibre in plant-based foods and are also used as stabilizers and thickeners in cosmetics and pharmaceuticals. See also glycocalyx; mucigel.