Sclereids are highly thickened dead sclerenchyma cells with very narrow cavities. They may also be branched. They provide stiffness to the parts in which they occur. Sclereids are of many types: brachysclereids, macrosclereids, osteosclereids, astrosclereids, trichosclereids and filiform sclereids. Astrosclereids are star-shaped, having various branches or arms. They are found in intercellular spaces of leaves and stems of many hydrophytes like Nymphaea.