Figs. 6 and 7. Light micrographs of longitudinal sections through tissue undergoing dedifferentiation during generation of new phellogen after mechanical wounding of bark of healthy 2-year-old peach bark. Outside bark in all figures is oriented toward top of plate. Bar = 10 microns. Figs. 6 and 7 show bark tissue stained with phosphine, under bright field and the same under ultraviolet excitation, respectively, showing impervious tissue (IT), first phellem (PH), and newly regenerated phellogen (PG) 7 days postwounding. Note in Fig. 7 the thin suberin lining of the cells in the impervious zone (small arrows).