The vascular bundle in which the xylem is in the center and the phloem surrounds it or the phloem is in the center and the xylem surrounds it is called a centric vascular bundle. It is of two types.
(i) Hadrocentric : A vascular bundle in which xylem is in the center and phloem surrounds it is called hadrocentric or amphicribal. Like- Lycopodium, Selaginella, Pteris, Psilotum etc.
(ii) Leptocentric: A vascular bundle with phloem in the center and xylem surrounding it is called leptocentric or amphivascular. Such as Dracaena, Yucca etc.
Function of Central Vascular Bundle: Xylem transports water and mineral salts. Phloem transports food. It gives strength to the plant. Provides mechanical energy to plants.