When phloem is surrounded by xylem ______________.
When the phloem surrounds the xylem tissue completely. The vascular bundle is known as an amphicribal vascular bundle or an androcentric type. Such vascular bundles are possible in pteridophytes.
In the Concentric bundle, xylem either encircles or is encircled by the phloem. Accordingly, the Amphivasal bundle is a vascular bundle in which xylem encircles the central strand of phloem and it is called amphivasal bundle or leptocentric bundle.
In the conjoint, these vascular bundles xylem and phloem are present on the same radii.
A collateral arrangement is having xylem and phloem next to each other.
So, the correct answer is 'Concentric leptocentric/amphivasal.
The correct option is B.