Relevance. The need to identify new diagnostic features in the structures of related fossils and modern plants. Molecular paleontology as an independent direction has proved itself well in the part of studying fossil representatives of plant and animal world. Aim. The study of phytoleims and herbariums by IR spectra of diffuse reflectance after their processing by the ASPECT programme complex is a part of the structural cluster analysis of carbonized substances methodology. It allows obtaining the results of structure-group analysis in the form of calculation of the number of functional structural units – structure-forming clusters from elements C, N, H, O and their quantity in the form of elemental composition C-C, C-N, C-H, C-O, N-H, N-O. Objects. Samples of the recent and Middle-Late Jurassic mosses, horsetails, ferns and ginkgoopsids. Methods. Morphological, epidermal-cuticular, infrared spectrometric. Results and conclusions. It was established that at the expense of a part of C-N and C-O bonds there is recombination of phytoleims of mosses, horsetails, ferns and ginkgoopsids into C-H, N-H, N-O bonds. The molecular difference between leaf and stem of horsetail and fern is different. In horsetails, the number of functional structural units vCCN and vOCO is the distinguishing feature, while in the main features are the vCC and δNH clusters, and this structural feature can serve as a diagnostic criterion in molecular palaeobotany. A comparative analysis of coal and phytoleimma of horsetails of the Equisetites sp. from boreholes in the Snezhnaya area in the Tomsk region showed that the structure of the carbonized substance of buried horsetails in the underlying sediments in terms of the number of C-C, C-N, C-O, N-H bonds does not differ much from the structure of coals concentrated above in the form of a thin layer. This may indicate that this coal is formed by horsetail residues. The only sign of difference may be CH-bonds, which are quantitatively smaller in coal.