The bark of a tree has epidermal tissue, and It is the outermost layer of the cell that covers the whole plant. The bark of trees is brown and younger stems are green.
- As plants grow older, the outer protective tissue undergoes certain changes.
- A strip of secondary meristem replaces the epidermis of the stem.
- Cells on the outside are cut off from this layer.
- This forms the several-layer thick bark of the tree.