The use of inertinite macerals as palaeoenvironmental and palaeodimatic indicators is reliant on understanding their origin. Criteria to distinguish between carbonisation and pyrolysis, or saprotrophy resulting from fungal degradation, are not always clear. Without the presence of primary particles in coal, such as fungal sclerota, hyphae, char, and fly ash, the origin of inertinites is difficult to distinguish. This short study provides an insight into basic anatomical characteristics, which differentiate saprotrophied and carbonised inertinite group macerals. Modern plant matter and Permian phyterals are compared petrographically to observe changes in the macerals at a cellular level. Saprotrophic effects include thickening of the cell wall and cellular damage, delignification of the cell wall and cross ray piths, and the irregular oxidation radiating from xylem tissues. These characteristics are not observed in carbonised inertinites that show enlarged ray cells and the shrinking and homogenisation of cell walls. The simple differentiation between these characteristics in inertinites can greatly affect the palaeoenvironmental interpretations linked to the presence of inertinites in coal. (C) 2014 Elsevier B.V. All rights reserved.