Permanent tissues are composed of cells that have lost the power of division, having attained their definite form, size, and shape.
On the basis of constituent cells, permanent tissues can be classified into three categories: simple tissue, complex tissue, special tissues.
Simple tissues are homogeneous and composed of only one type of cell. On the basis of the structure of constituent cells, three types of simple tissues are parenchyma, collenchyma, sclerenchyma.
While Xylem is the example of complex tissues.