Solution:

Periderm:-                             

A periderm is a group of cells through which the best of both kinds of tissues i.e., living and dead can be witnessed.

They are the secondary tissues that replace the primary tissues towards the outward bark.

It consists of cork cambium, phelloderm, and cork cells.

In dicot plants, the formation of the periderm is carried out with the help of a cambial ring, due to which the cortex gets distorted. When the cortex is distorted due to which the phellogen and phelloderm formation take place by differentiation. The phellogen is a meristematic tissue found towards the outside that actively keeps dividing and helps in increasing the girth of the plant. The phelloderm is present inside the cambium which are permanent tissues that are pushed to the inside forming the rings through which we count the age of the tree.