When xylem and phloem are present in the same radius and separated by a strip of cambium in the vascular bundle, such bundles are described as 

In dicotyledonous stems, cambium is present between phloem and xylem. Presence of cambium possess the ability to form secondary xylem and phloem tissues, and hence are called open vascular bundles. If the xylem and phloem are situated on the same radius of vascular bundles, then they are called conjoint and collateral type of vascular bundles.