Tissue

Anatomy is the branch of botany that deals with the internal structure of a plant, as opposed to morphology, which deals with external form. Every organ of a plant — root, stem, leaf, flower — is built from groups of cells, and a tissue is defined as a group of cells that share a common origin and work together toward a common function, whether or not the individual cells look identical.

Plant tissues are broadly sorted into two categories purely on the basis of one property: whether their cells retain the ability to divide.

• Meristematic tissue — cells that continue to divide throughout the life of that region.
• Permanent tissue — cells that have divided their last division and settled into a fixed shape, size and job.

Every tissue described in this chapter, and every anatomical feature of a root, stem or leaf, is ultimately built from one or the other of these two categories, so this division is the organising idea for the whole chapter.