(N/A) The cambial ring becomes active and begins to cut off new cells,both towards the inner and the outer sides.
The cells cut off towards the pith mature into secondary xylem,and the cells cut off towards the periphery mature into secondary phloem.
The cambium is generally more active on the inner side than on the outer side. As a result,the amount of secondary xylem produced is more than the secondary phloem,and it forms a compact mass.
Due to the continuous formation and accumulation of secondary xylem,pressure is exerted,which gradually crushes the primary and secondary phloem.
The primary xylem,however,remains more or less intact in or around the center.
At some places,the cambium forms a narrow band of parenchyma,which passes through the secondary xylem and the secondary phloem in the radial directions. These are the secondary medullary rays.