Vascular cambium possesses two distinct types of initials, ray initials forming medullary rays, and fusiform initials producing xylem and phloem elements.

• 维管形成层具有两种明显的分生组织，射线原始细胞形成了髓（还应包括维管射线，译者注）射线；纺锤状原始细胞形成了次生木质部和次生韧皮部。