Correct Answer - C
In order to provide increase in girth and prevent repturing of the outer ground tissues due to the formation of secndary vascular tissues, icot stems produce a cork cambium or phellogen in the outer cortical cells. The cells of this phellogen divide periclinally to produce phellem or cork on the outer side and secondary cortex or phelloderm on the innter side. phellem, phellogen and phelloderm collectively constitute periderm.
