The conjoint vascular bundles with only inner phloem and outer xylem are

In leptocentric or amphivasal vascular bundles, the phloem is at the centre and surrounded by xylem. In collateral vascular bundles and hadrocentric vascular bundles, the phloem is outside and xylem is towards the center. In bicollateral vascular bundles phloem is present towards the periphery as well as towards the center.