Origin and Formation of Vascular Cambium

The vascular cambium of a dicot stem does not arise from one single source - it is assembled from two structurally different starting tissues that eventually join into one continuous ring. Inside each vascular bundle, a strip of cambium believed to originate from the procambium is already present, sandwiched between the primary xylem and primary phloem; this is called the intrafascicular (or fascicular) cambium, and because it develops from the procambium it starts out as part of the stem's primary meristem. Between the vascular bundles, by contrast, some of the parenchyma cells of the medullary rays - specifically those lying in line with the intrafascicular cambium - become meristematic on their own and form new strips of cambium called the interfascicular cambium; because these cells only turn meristematic later, from ordinary ground tissue, interfascicular cambium is secondary in nature from the very start. Once formed, the interfascicular cambium joins up with …