#actinostel

• 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.
• Asteroxylon — A genus of primitive fossil plants (Asteroxylon) from the Lycopodiopsida class, characteristic of the Early Devonian, discovered in the famous Rhynie chert deposits (Scotland); they were ancient terrestrial plants with dichotomously branched stems covered with scale-like leaf-like outgrowths (enations) and featuring a star-shaped central cylinder (actinostele) visible in cross-section.