Periclinal divisions in the pericycle that are not involved in the formation of the vascular cambium occur not only outside the xylem poles, but spread around the circumference of the root. Such divisions are preparatory for the formation of the periderm. A phellogen arises among the outer cells of the proliferated pericycle which forms cork tissue to the outside and phelloderm towards the inside. The phelloderm is difficult to distinguish from the parenchyma derived from the pericycle.