ИСТИНА

Permineralised stems are rarely found in the Lower Carboniferous deposits of Russia. There are only three regions where different permineralised stems of the arborescent plants were ascertained. A number of lycophyte underground stems of Stigmaria ficoides (Sternb.) Br. with preserved anatomical structure were fixed from the Upper Visean of the Novgorod region. They were preserved as pyritous concretions in coaly clays. The pith of S. ficoides is hollow, surrounded by an endarch primary xylem. The secondary xylem is divided by pith rays on 14–18 wedges composed of the tracheids. The rays are of two types: simple, and complicated. Besides lycophytes, partially petrified specimens of stem fragments of arthrophytes - Archaeocalamites radiatus (Br.) Stur were found in the Upper Visean sandstone layers of the Novgorod and the Tula regions. They show tracheids of the secondary xylem with small wide pits only on radial walls and narrow rays with rectangular ray cells. A few of anatomically preserved stem and root fragments of A. radiatus were also found in the Upper Visean from the north of the Arkhangelsk region. It is particularly important to note, that a lot of findings of permineralised stem portions were recognized from ferruginous sandstones from the Lower Carboniferous of North Russia. In the first instance, the stem fragments of arborescent plants of a lignophyte affinity - Eristophyton sp. with well-preserved secondary xylem were fixed from different localities of the Arkhangelsk region. Metaxylem tracheids of Eristophyton sp. show scalariform thickening both on radial and tangential walls. The secondary xylem has polygonal narrow tracheids and short rays. The tracheids of the secondary xylem have uni- and multiseriate araucarioid pitting only on radial walls. The pits are with inclined split-like apertures. The xylem rays are uni- and biseriate. Cross-fields show mainly few rounded pits with inclined apertures. Another finding of permineralised stem fragments was revealed to the north of the Arkhangelsk region. A new wood is represented by a well-preserved structure of the secondary xylem with narrow polygonal tracheids and short, only uniseriate xylem rays. Tracheids of the secondary xylem show only uniseriate pitting both on tangential and radial walls. The tracheid pits have circular pores. Thus, at least four different types of permineralised stems of lycophytes, arthrophytes, and lignophytes were recognized in the Lower Carboniferous of European part of Russia.