Vitrinite occurring as large phytoclasts is the dominant phase in a high proportion of the organic matter (Table T3). Most of these large phytoclasts show excellent preservation of the cell structures (Plates P1, P2, P3, P4, P5, P6). The textures range from textinite (less common) to texto-ulminite (most common) and ulminite (common). Bark tissue is present, and suberinite is found there in association with phlobaphinite.
Where distinct cell structures are present, the cell contents almost all have a higher reflectance compared with the cell walls. The ratio of the reflectance of the cell contents to that of the cell walls is typically between 2 and 3 to 1. Thus, most cell contents show reflectances between 0.3% and 0.4% and the cell walls between about 0.08% and 0.18%. Typical cell structures are shown in Plate P1. The contrast between texturally immature vitrinite (Plate P2, fig. 1, fig. 2) and texturally mature vitrinite (Plate P2, fig. 3, fig. 4) is shown in Plate P2.
Plates P3 and P4 illustrate the unusual very low reflecting and strongly fluorescing primary cell wall tissues found in some wood structures. Medullary rays are present in the fields illustrated in Plate P3, and they represent xylem tissues. Such a large reflectance and fluorescence contrast is not normally associated with xylem tissues. Plate P4 illustrates the variable amounts of low-reflecting tissue. The mean reflectance for the field in Plate P4, figure 1, would be evenly weighted between the higher reflecting cell contents and the cell walls. In the field in Plate P4, figure 3, the mean would be heavily weighted toward the low-reflecting cell walls.
Some of the low-reflectance cell walls are transitional to suberinite. Some of these fields are illustrated in Plate P5. Plate P6 illustrates suberinite tissues and also shows the effects of prolonged irradiation on both the cell walls and cell fillings. Fluorescence intensity is increased on prolonged irradiation, and the reflectance of both the cell walls and contents is lowered. Plate P6, figure 3 and figure 4, illustrate cuticle tissues present on woody tissues. This type of cutinite is similar chemically but differs in tissue associations from the leaf cutinite illustrated in Plate P13, figure 1 and figure 2.
Where cell structures are well defined (as in Plates P1, P3, P4, P5), it is possible to selectively measure the reflectance of cell contents and these are considered to be more representative of maturation (coal rank) compared with the values obtained from the cell walls. However, in many fields, similar tissues appear to be present but the cell walls cannot be separated from the cell contents. Plate P2, figure 3, shows a tissue with a range from 0.54% to 0.24%. Some of these differences are related to the contrast between cell walls and contents, but at least three major different tissue layers can be distinguished in this field. In the field illustrated by Plate P7, figure 4, and Plate P8, some cell outlines are shown by pyrite inclusions but no major differences can be seen between cell contents and cell walls. However, the lower layer shows a reflectance of 0.26% and the upper layer 0.48%. Although the vitrinite in Plate P2, figure 4, is very low in rank, the textures are essentially those of telocollinite, a maceral normally considered as being restricted to the bituminous rank range.
Overall, it is clear that tissue type exerts a major influence on the mean reflectances obtained. Where cell walls can be distinguished, it is possible to minimize this variation by restricting measurements to the cell contents, as these proved to show less variation. However, for many samples, low-reflecting tissues are present that do not show cell structures. In a small proportion of samples, these low-reflecting homogeneous tissues are the only population present. Thus, it was not possible to eliminate the effects of tissue type on the reflectances obtained.