Cells which takes part in secondary growth are named as

Cambium, in plants, is a layer of actively dividing cells between xylem (wood) and phloem (bast) tissues.
It is responsible for the secondary growth of stems and roots (secondary growth occurs after the first season and results in an increase in thickness).
Hence, Cells which takes part in secondary growth are named as Cambium.
So, the correct answer is 'Cambium'.