ИСТИНА

The stem fragments of the Early Carboniferous arborescent plants of a lignophyte affinity with a well-preserved secondary xylem were fixed from different localities of the Moscow Syneclise (Central Russia). Anatomical features of the woods have been studied with a scanning electron microscopy (SEM CAMSCAN). The fossil wood of Pycnoxylon was ascertained from the Upper Visean of the Novgorod region. It was preserved as a pyritous concretion in sands. The secondary xylem of Pycnoxylon is of a pycnoxylic type of the wood. In the radial section the polygonal tracheids are narrow (18-48 μm in diameter) and relatively long (up to 1000 μm). The tracheids of the secondary xylem have uni- and multiseriate bordered pitting on radial walls, and uniseriate pitting on tangential walls. The pits on radial walls are rounded and hexagonal in outline; 8 – 12.5 (average 10) μm in diameter with inclined narrow-elliptical apertures. The xylem rays are from uni- to multiseriate (up to four cells wide), relatively high – 2 – 41 (commonly 14-23) cells in height. Cross-fields show 4 – 12 (average 7) rounded hexagonal pits with inclined apertures. Earlier genus Pycnoxylon was described by J. Cribbs (1938) only from the Reed Spring Formation of Missouri (USA). Another finding of permineralised stem fragments was revealed in the Tula region (the Lower Visean deposits). A new wood is represented by a well-preserved structure of the secondary xylem with narrow long tracheids (25-48 μm in diameter) and short, uniseriate, rarely biseriate xylem rays. Tracheids of the secondary xylem are with uni-multiseriate pittings (commonly biseriate) only on the radial walls. The pits are hexagonal in outline, 7-11 μm in diameter. The xylem rays are up to 13 cells high (average 5.2 cells). Cross-field pitting is of window-like type, which is typical to pinaceous wood. Most features of this wood are similar to ones of the wood of Eristophyton sp., known from the Lower Carboniferous of North Russia (Arkhangelsk region) and France (Vosges). However, unusual for the Early Carboniferous woods cross-field pitting points out the relationship with pinaceous plants. Thus, the new findings of permineralised stems in the Lower Carboniferous of the Moscow Syneclise show two different types of fossil wood firstly found in Russia.