A vascular bundle that has xylem in the middle and phloem on both sides is called a bicollateral vascular bundle. These vascular bundles have xylem in the middle and exocambium on the outside and endocambium on the inside. Correspondingly, there is exophloem outside the exocambium and endophloem inside the endocambium. Dicotyledonous plants have equilateral vascular bundles in their stems. For example, gourd, pumpkin, cucumber etc.