Explain how formation of cambial ring occurs in dicot stem.

1. The cambium present between the primary xylem and primary phloem of a vascular bundle is called intrafascicular cambium.

2. With the onset of favourable season, meristematic cells of intrafascicular cambium become active. 

3. Simultaneously, the ray parenchyma cells, both fusiform initials and ray initials become meristematic. This is known as dedifferentiation. 

4. These form patch of cambial cells (meristematic cells) in between the adjacent bundles and produce interfascicular cambium. 

5. Both intrafascicular and interfascicular cambium join and form a complete ring, known as the cambial ring. This is possible because they lie in one plane.