Fig. 24. Transmission electron micrographs of transverse sections of the boundary zone and necrophylactic periderm of wounded peach bark. Bar = 1 micron. Fig. 24 shows portion of necrophylactic phellem showing at bottom right a portion of the lumen and shared wall of the external phellogen daughter cell (PDC), the most recently derived suberized phellem cell (P1) with thin suberized secondary walls (S), and two older phellem cells (P2 and P3) showing thick suberized secondary walls (S) and senescing cell cytoplasm.