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in plants, a change in the cell walls caused by lignin, which fills the interstices between the microfibrillae of cellulose. Lignification begins with the middle lamella (the primary membranes of two neighboring cells with an interlayer of intercellular matter) and then spreads to the secondary wall. As a result of lignification, the wall becomes hard and resistant to microorganisms and fungi but loses its elasticity. Lignification of cell walls is characteristic of all higher plants except mosses. The mechanical strength of wood and sclerenchyma, which consist of lignified cells, depends on the volume and distribution of the cells in the plant organs.