Collateral vascular bundle :
(i) A conjoint vascular bundle in which the phloem lies towards outer side (i.e., towards periphery) and xylem lies towards inner side (i.e., towards centre).
(ii) If open, the collateral bundle usually has a cambium strip in between phloem and xylem.
Bicollateral vascular bundle :
(i)A conjoint vascular bundle in which the one phloem patch lies towards outer side and the other phloem patch lies towards inner side. The xylem patch lies in between the two patches.
(ii)Bicollateral bundle has two strips of cambium, outer and inner (on both the sides of xylem).