Plate P4. Variable contribution of cell walls to the bulk of vitrinite. 1. T5809; Hole 1109D; 387.86 mbsf. Woody tissue preserved as vitrinite but with the volume of the cell walls close to that of the cell lumens. The corpocollinite within the lumens has a much higher reflectance compared with the cell walls, and its optical properties provide a more reliable measure of coal rank than the optical properties of the cell walls (reflected light; field width = 0.22 mm; vitrinite reflectance [cell contents] = 0.34%).