Pelargonium the first periderm

The micrograph to the left, illustrates the position and relationship of the first periderm and its components. Working from the outside, the epidermis is mostly missing, and the 8-9 rows of cells visible here are the phellemm (P). Beneath this, is a layer of cells - reminiscent of a cambium which is in fact, the phellogen (PG)or generative (cambium-like) layer that produces the phelloderm (PD) to the inside (endarch to itself), and the phellem to the outside (exarch to itself). Notice that the phellem cells are changing colour - suggesting that waxes and other substances are beginning to be deposited in this important protective layer