File:Woody Dicot Stem Vascular Cylinder in One Year Liriodendron (35879582273).jpg

cross section: Liriodendron stem magnification: 100x

During the first year of growth the underling activity of the cork cambium begins to replace the cutinized epidermis and outer cortical tissues with a protective layer of cork rich periderm. The outermost layer of periderm consists of layers of cork cells, the phellem, which produce the waterproofing substance suberin. Cork cells are dead at maturity.

Deep to the phellem is a layer of living cork cambium or phellogen and just beneath that layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. 

Deep to the periderm is a narrow cortex of parenchyma cells.

The vascular cylinder consists of a narrow outer ring of primary phloem, a middle single layered ring of vascular cambium and a deeper large ring of primary xylem. Phloem wedges of sieve tubes and companion cells are layered and interspaced with masses of thick walled sclerenchyma cells, and conspicuous caps of sclerenchyma top each wedge of phloem.

The cells of the deepest protoxylem are small, thin walled and separated from the pith by a starch sheath of dark staining parenchyma cells. Metaxylem cells above are larger, heavier walled . Xylem cells of the later wood are smaller and thicker walled.