Secondary Growth in a Typical Dicotyledonous Stem

In stem, the secondary growth in thickness in diameter is confined both intrastelar, i.e., in the stele and extrastelar regions. The cells that make secondary tissues are generated by lateral meristems. The lateral meristems grow and join to make a circular ring known as the vascular cambium which lays down cells that become the secondary vascular tissues. In the stem, cells that are situated among the primary xylem and primary phloem in the, vascular bundles turns into meristematic and make part of the vascular cambium. Additional cells between the vascular bundles also become meristematic. Hence the vascular cambium can be seen in a cross section of the stem as a continuous ring of tissue, with the xylem and pith on the inside and phloem, cortex, and epidermis on the outside

Figure: Diagrammatic Representation of Secondary Growth in a Typical Dicotyledonous Stem