The tissues in which the power of division of cells is lost, either permanently or temporarily called permanent tissues. Permanent tissues develop from the derivatives of various meristems. The permanent tissues have the following features:-
(i) Protoplasm may be present or absent in the cells at maturity.
(ii) Cell wall is thin or thick but there is no formation of secondary cell wall.
(iii) Cell wall is composed of substances such as lignin, hemicellulose, etc. in addition to cellulose.
(iv) Intercellular spaces may be present.
(v) Cells contain ergastic substances.
(vi) Metabolic activities are relatively slow.
Permanent tissues may contain cells which are all similar and such tissues are called simple tissues. Tissues may contain cells which differ from each other in structure and are called complex tissues. But irrespective of similarities or dissimilarities, the component cells of any complex tissue have a common origin.
Permanent tissues are divided into two types depending on the structure and arrangement of the component cells. They are simple tissue and complex tissue. Some workers consider secretory tissue as a third type of permanent tissue but according to Esau (1947), secretory tissue is an aggregation of cells from the morphological view point (an apparent tissue). The component cells very often do not have a common origin and morphological continuity.