Amphicribral

Amphicribral refers to a specific arrangement of vascular tissues found in the stems of certain plants, particularly those with a siphonostele. In this arrangement, the xylem and phloem are situated in a concentric cylinder, with the phloem surrounding the xylem. This is in contrast to other vascular bundle arrangements like collateral, where xylem and phloem are side-by-side. The amphicribral structure is considered a specialized adaptation, often seen in the stems of ferns and some other Pteridophytes. This arrangement is believed to facilitate efficient transport of water and nutrients throughout the stem. The term amphicribral is derived from Greek roots, with "amphi" meaning "on both sides" or "around," and "cribrum" meaning "sieve," referring to the sieve elements of the phloem. Understanding this vascular organization is important in plant anatomy and morphology, contributing to the study of plant evolution and adaptation.