The sample in the formof the drill core 9 cm long and 6 cm in diameter reveals exclusively secondary wood. No growth rings have been observed. Tracheids have the width 20–50 μm (mean 25 μm) in the tangential section. Pitting on the radial walls is mainly uniseriate, partly biseriate or triseriate. The uniseriate pits are circular or oval. The biseriate and triseriate pits are polygonal (often hexagonal), distributed adjacent to each other, and densely cover the whole width of the walls. The diameter of the pits is 12±2 μm. The poruses are circular. Medullary rays are mostly uniseriate, composed of 1–46 layers; mostly between a fifteen or so and 30 layers. As the investigations are at the preliminary stage, the author prefers to use only the generic term to name the wood, namely Dadoxylon sp., without giving it a species designation. Mineralogical investigation of silicified wood was conducted using polarizing light microscope. Observations showed various the optical orientation of quartz crystals filling up cells of wood. It is observed as differentiated disapperance of polarized light. This phenomenon documents that beginning of growth of quartz crystals (center of crystallization) was located at various places of cell walls. This situation is the result of beginning of destruction of organic compounds of wall structure of cells at various places. Additionally investigation documents various intensity of silification of cordaitalean structure. Because of this the process of silification is different at various parts of tissues and one can observe parts fully petrified and completely without mineralization. The structure of wood tissues is at same places damaged by crystallizing quartz. This phenomenon is observed at the tissues where silification was continued and size of newly formed quartz crystals is overgrowth size wood cells of wood. Mentioned zones of cell destruction are especially well seen at placed where silification developed parallel to orientation of biological wood structures. In summary one can say that mentioned processes were the reason of only partial petrification (silification) of examined cordaitalean second wood.
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