A portion of vascular tissue (PO:0009015) that is a unit strand of the vascular system (PO:0000034) and has as part xylem (PO:0005352) or phloem (PO:0005417). [source: POC:curators]
Comment
May also contain portions of ground tissue (PO:0025059). The bundle sheath (PO:0006023) can also be part of a vascular bundle, if it is present.