Vessel member above, parenchyma cell below. The primary wall is partly hydrolyzed in the vessel member. Protoplasmic residue covers the secondary and hydrolyzed primary wall. The wide spaces between the sections of the cells indicate that the cell had undergone considerable stretching. In the vessel member to the right the degradation of the primary wall is almost complete and cytoplasmic residue is left in the cell.
Open arrows indicate the connection between the primary and the secondary walls.
Later stage of end wall degradation. A rim of secondary wall material has been deposited around the margin of the end wall delimiting the future perforation. The electron lucent condition of the primary wall layers has extended to the rim. It has been accompanied by thickening of the part of the end wall that has to be removed. The part of the end wall not covered by the rim has been removed.