Also found in: Medical.
concentric bundle[kən′sen·trik ′bən·dəl]
A vascular bundle in which xylem surrounds phloem, or phloem surrounds xylem.
a bundle of conducting tissues of xylem and phloem in the stems and leaves of several ferns and angiosperms. In an amphicribral bundle, the phloem surrounds the xylem. In an amphibasal bundle, the xylem surrounds the phloem.