A peripheral portion of ground tissue in a plant axis that is composed of phellogen, phellem, and phelloderm. [source: ISBN:047124529, POC:curators]
Comment
After secondary growth, the periderm may replace the epidermis in stems and roots, rarely in other organs. In some cases, the epidermis is retained after periderm development. Periderm is derived from lateral meristem and may contain secondary phloem.