The new state is stabilized by the simultaneous working-in of additional wall material. The other truly supporting tissue is the sclerenchyma. Sclerenchyma cells are the principal supporting cells in plant parts that have ceased elongation. It is their hard, thick walls that make sclerenchyma cells important strengthening and supporting elements in plant parts that have ceased elongation. The difference between fibres and sclereids is not always clear.
Transitions do exist, sometimes even within one and the same plant.
Fibres are generally long, slender, so-called prosenchymatous cells, that occur usually in strands or bundles. Such bundles or the totality of a stem's bundles, for example, are colloquially called fibres. Their high load-bearing capacity and the ease with which they can be processed, has since antiquity made them the source material for a number of things, like ropes, fabrics or mattresses. Their principal cell wall material is cellulose. Contrasting are hard fibres that are mostly found in monocots.