SUMMARYThis paper describes the occurrence of plant‐cell structures retained in particles of the principal coke‐forming constituent (vitrinite) of a coking coal, which has passed through its decomposition point during carbonization using several rates of heating. The benefits of wider application of the study of organic constituents with high optical absorptions under crossed polars in reflected light are emphasized. Relief‐polished surfaces of certain of the vitrinite‐char particles, which appear virtually structureless in plane‐polarized light under oil immersion, when viewed under crossed polars not only possess well‐preserved plant‐cell structures, but also show development of a mosaic structure from a mesophasein situwith virtually no disturbance of even the cell walls. Retention of the original cell structure is almost certainly governed by a reduced reactivity of this vitrinite induced by oxidation of the original plant tissues at the time of their deposition in the coal
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