Vascular bundles are components of the vascular tissue system that consist of two main parts i.e.xylem and phloem. In which xylem is called water-conducting tissue and phloem is called food conducting tissue. The vascular bundles can be of two types like radial and conjoint. Conjoint further subdivided into collateral, bicollateral, and concentric. 
 In dicotyledonous stems, cambium is present between phloem and xylem. Such vascular bundles because of the presence of cambium possess the ability to form secondary xylem and phloem tissues, and hence are called open vascular bundles.