Describe the vascular cambium responsible for secondary growth in detail.

(N/A) $\rightarrow$ Vascular Cambium: The meristematic layer responsible for the formation of two conducting tissues,xylem and phloem,is called the vascular cambium.
$\rightarrow$ In young stems,it is present in patches as a single layer between the xylem and phloem. Later,it forms a complete ring.
$(a)$ Formation of Cambial Ring: In dicot stems,the cells of the cambium present between primary xylem and primary phloem are known as intrafascicular cambium. The cells of medullary rays adjoining these intrafascicular cambium become meristematic and form the interfascicular cambium. Thus,a continuous ring of cambium is formed.
$(b)$ Activity of Cambial Ring: The cambial ring becomes active and begins to cut off new cells towards both the inner and outer sides.
$\rightarrow$ The cells cut off towards the pith mature into secondary xylem,and the cells cut off towards the periphery mature into secondary phloem.
$\rightarrow$ 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 secondary phloem,and it soon forms a compact mass. At this point,secondary xylem becomes the main part of the stem.
$\rightarrow$ The primary and secondary phloem get gradually crushed due to the continued formation and accumulation of secondary xylem.
$\rightarrow$ The primary xylem,however,remains more or less intact in or around the center.