Several bacterial pathogens of potato tuber cannot infect from the wound about 8 hours after wounding. When the sections of the wounded part of potato tubers were dipped in 50% H2SO4 and examined by the microscope, oil-drop-like substances emerged in the cells of parenchymatous tissue (Fig. 3). In 3~8 layers of the cells, which lay under the cut surface, those oil-drop-like substances changed their forms gradually after wounding. being spherical at first. somewhat amaeboid at 2~4 hours, somewhat fibrious at 4~6 hours, and membraneous at 8~12 hours later respectively (F.g. 2). About 10 days after wounding, those transformations were recovered. The spherical oil-drop-like substances appeared again in all cells, with the exception of a layer of cells under the wound cork cambium. Above phenomena were also found out in the cells around the vascular bundles, which lay far from the site of wounding. The stimulation of the wounding seemes to spread by the aid of the vascular bundles (Fig. 4). The formation of suberised deposit has no connection with that of subcrin and lignin (Table 1 and Table 2). All of them are seemed to be formed too late to prevent the wound infection of bacterial pathogens of potato tubers (Fig. 1).