Figs. 2.13-2.20. Transverse sections of peach bark examined with ultraviolet epifluorescence illumination (Figs. 2.13 - 2.17, bar = 10 m) and transmission electron microscopy (Figs. 2.18 - 2.20, bar = 1 m). In Figs. 2.13-2.16, the wound surface is approximately 800 microns above the noted cellular changes. Note the presence of phloem fibers (F) in Figs. 2.14-2.16. Fig. 2.13. Nonwounded control tissue showing ray parenchyma in the region of primary and secondary phloem. Note the lack of autofluorescence. Fig. 2.14. Tissue 6 days postwounding. First traces of lignin autofluorescence are in the cell corner-middle lamella region of boundary zone cells (arrows) immediately external to living tissues (LT). Fig. 2.15. Tissues 8 days postwounding. Note deposition of suberin linings (arrows) in boundary zone cells and the dedifferentiation of internal tissues in the process of forming new phellogen (LT). Fig. 2.16 . Tissue 12 days postwounding showing a completely differentiated necrophylactic periderm with phelloderm (PD) and two to four layers of phellem cells (NP). Fig. 2.17. Tissues 14 days postwounding, showing a completely differentiated necrophylactic periderm with three to five phellem cell layers (NP) and newly differentiated phelloderm (PD). Figs. 2.18-2.20. Transmission electron micrographs of transverse sections of peach bark boundary zone tissues. Fig. 2.18. Portion of boundary zone cell 8 days postwounding with suberin lining (S) adjacent to a nonsuberized cell (NSC). Plasmodesmatal canals (P) in shared cell wall (CW) appear more electron dense than suberin. Suberin appears only slightly lamellate and is relatively electron lucid. Fig. 2.19. Shared cell wall of two adjacent cells in the boundary zone 12 days postwounding. The compound wall (CW) is very electron dense. Suberin linings (S) are of uniform thickness within individual cells and vary in thickness among cells. Note the fine light and dark lamellations of the suberized wall and the cytoplasmic debris (CD) appressed to the wall of the upper cell. Fig. 2.20. High magnification view of suberized cell wall in the boundary zone showing the fine light and dark lammelations characteristic of suberin.