Plate P4. Variable contribution of cell walls to the bulk of vitrinite. 2. T5809; Hole 1109D; 387.86 mbsf. Same as figure 1, but in fluorescence mode. The cell walls show moderate to strong fluorescence, and moderate positive alteration of the fluorescence was noted on prolonged irradiation. The section is close to being a transverse section of the wood. The larger areas of fluorescence in part indicate sections parallel with a cell wall and in part zones where corpocollinite has not filled the cell lumens (reflected light; field width = 0.22 mm; vitrinite reflectance [cell contents] = 0.34%).