Colour enhanced light micrograph of the cross section of a Tilia sp. stem. The stem is three-years-old as it has three growth rings (concentric circles). The following is depicted (from outer to inner circle): epidermis (dark green edge), primary and secondary phloem (dark maroon section) with pith rays (green triangular parts in phloem), primary and secondary Xylem (lighter sets of rings), and Pith (green portion in centre).