A * stele containing a central core of pith internal to the xylem. The pith may be extrastelar in origin, i.e. originating from invagination of cortical parenchyma, or it may originate in the xylem itself. In a simple siphonostele the leaf traces do not leave any gaps in the vascular cylinder. A siphono-stele may be ectophloic, i.e. possessing phloem external to the xylem, or amphiphloic, i.e. possessing phloem both external and internal to the xylem as in a * solenostele. Siphonosteles are found in the stems of many ferns. Compare protostele. See also medullated protostele. |
