Sclerenchyma is the lignified supportive simple permanent tissue composed of thick-walled & dead cells as their living protoplast is absent in the cells.
Sclerenchyma consists of the sclerenchyma fibers & sclereids.
Sclereids are also typically found in the epidermis, ground tissue, & vascular tissue.
Sclereids are roughly isodiametric in shape, and clumps of these cells are referred to as “stone cells”.