#protostele
- 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.