Xylem and phloem in young roots

(1) Example of a transverse section in a primary root of Caltha palustris a dicotyledon. In the vascular cylinder we observe 5 protoxylem poles (1 to 5) forming a star with alternating regions of phloem (ph). Metaxylem is external to protoxylem and located toward the center. It is composed of large elements. See also the page : root of Caltha p.

(2) Transverse section in a primary root of Iris, to illustrate the distribution of xylem and phloem in a primary monocotyledon root. 
The vascular cylinder contains a larger number of xylem and phloem elements than in Caltha palustris. In this section we observe twelve poles of xylem (1 to 12)  alternating with phloem. Protoxylem is located towards the outside in contact of pericycle and large elements of metaxylem are orientated towards the center of the vascular cylinder. See also the page: root of Iris.