(from the article `fern`) ...the original fern stem was protostelic (its stele having no pith or leaf gaps), but this is not necessarily true of the immediate ancestor of ...
When a plant's vascular tissue develops in discrete bundles, it is said to have a eustele. See also protostele and siphonostele.
When a plant's vascular tissue develops in discrete bundles, it is said to have a eustele. See also protostele and siphonostele.
an arrangement of the xylem and phloem in discrete strands, separated by areas of parenchymatous tissue.