All except $IV$.

On the basis of variation in form, structure, origin and development, sclerenchyma may be fibres or sclereids. The fibres are thick walled, elongated and pointed cells, generally occurring in groups, in various parts of the plant. The sclereids are spherical oval or cylindrical, highly thickened dead cells with very narrow cavity (lumen). These are commonly found in the fruit wall of nuts, pulp of fruit like guava, pear and sapota, seed coats of legumes and leaves of tea. Sclerenchyma provides the mechanical support to organs