It is a lateral meristem and contains fusiform initials giving rise to secondary xylem and phloem and ray initials giving rise to medullary rays.See also secondary growth.

• 维管形成层属于侧生分生组织，包括能够产生次生木质部与次生韧皮部的纺锤状形成层原始细胞和产生髓射线的射线原始细胞。