xylem and protophloem alone are differentiated) being very much shorter than in the stem.
the xylem being centrifugal and the m, Medullary bundles.
Differentiation of the xylem progresses outwards, of the phloem inwards, but the two tissues never meet in the centre.
The vascular bundles of the stem belong to the col xylem and the bast or phloem stand side by side on the same radius.
occasionally happens that groups of (After Worsdell.) xylem and phloem are developed pd, Periderm in leaf-bases.