How does cambium ring form in a dicot stem?

How does cambium ring form in a dicot stem?

In dicot stems, the cells of cambium present between primary xylem and primary phloem is the intrafascicular cambium. The cells of medullary rays, adjoining these intrafascicular cambium become meristematic and form the interfascicular cambium. Interfascicular and intrafascicular (PI. cambia) together form a ring of cambium called cambium ring.