sclerenchyma

Plant tissue whose function is to strengthen and support, composed of thick-walled cells that are heavily lignified (toughened). On maturity the cell inside dies, and only the cell walls remain.

Sclerenchyma may be made up of one or two types of cells: sclereids, occurring singly or in small clusters, are often found in the hard shells of fruits and in seed coats, bark, and the stem cortex; fibres, frequently grouped in bundles, are elongated cells, often with pointed ends, associated with the vascular tissue (xylem and phloem) of the plant.

Some fibres provide useful materials, such as flax from Linum usitatissimum and hemp from Cannabis sativa.