#phloem

• Actinostele — An archaic type of vascular cylinder (stele) characteristic of the stems and roots of primitive vascular plants (such as pteridophytes), representing a structural variety of protostele. In cross-section, the central xylem is not circular but features ridges or arms arranged in a radiating (star-like) manner, being fully encircled by a peripheral band of phloem, a configuration optimizing mechanical resistance and sap conduction.
• Amphiphloic — Having or characterized by the presence of phloem tissue on both sides of the xylem; an adjective used in plant anatomy to define a structural type of central cylinder (amphiphloic siphonostele or solenostele), commonly found in ferns, where the central pith is successively surrounded by an inner ring of phloem, a central ring of xylem, and an outer ring of phloem.