Collateral Vascular Bundles-
1. This type of vascular bundle is found in both dicot and monocot stems.
2. It is conjoint and may be open or closed type depending on the presence and absence of fascicular cambium.
3. Presence of one patch of phloem towards outer side and one patch of xylem towards inner side. A strip of cambium may or may not be present between phloem and xylem patches.
Example: Tridax, Zea.
Bicollateral Vascular Bundle:
1. It is confined to certain dicot stem only.
2. It is also conjoint but always open type due to presence of fascicular cambium.
3. It consists of two patches of phloem (outer and inner), two strips of cambium (outer and inner) one patch of xylem at the center.