Which cells are also known as …

Stone Cells   or sclereids, plant cells with considerably thickened, stratified, lignified, sometimes suberized or cutinized walls frequently saturated with calcium salts or silica and pierced by pore canaliculi. Mature stone cells have no live contents. Stone cells solidify tissues. The commonest are short stone cells, or brachysclereids, which are arranged in groups, or concretions, in fruit pith (pear, quince, chokeberry), rhizomes (peony, anemone), roots (horseradish), and phloem (oak, beech); less commonly, they form solid layers in the pericarp of nuts and acorns and cherry and plum pits. Elongated stone cells, or mac-rosclereids, usually form a solid layer in the seed coat (bean). Solitary stone cells, or idioblasts, are usually star-shaped (as-terosclereids) and found in fir bark, yellow water lily stems, and petioles; others extend from the top to bottom pellicle of a leaf, thereby making it tougher (tea, camellia).

Sclereids are also known as stone cells are a reduced form of sclerenchyma cells. It has highly thickened, lignified cellular walls that form small bundles of durable layers of tissue in most plants.