FIG. 5 in Anatomy, affinities, and evolutionary implications of new silicified stems of Sphenophyllum Brongniart, 1828 from the early Carboniferous (Mississippian) of France and Germany

FIG. 5. — Specimen with secondary growth from Puech de la Suque, Montagne Noire, France (MN864): A, slide MN864-C1, general view of the specimen in transverse section; the cortex is flattened but the central vascular tissues are not distorted; B, slide MN864-C1, central part of the axis in transverse section showing the cortex (C), the triangular shape of the primary xylem (X1), the position of the protoxylem (arrows), and a little development of secondary xylem (X2); a lacuna is present at the location of the protoxylem in the top right arm of the stele; C, slide MN864-C1, detail of secondary xylem (X2) in transverse section, with row of tracheids and possible ray cells (arrows); D, slide MN864-C1, more or less radial section through the stem showing the central part composed of primary and secondary xylem (X) and cortex (C); E, slide MN864-A5, detail of the box on element D showing possible tangentially elongated pits on the radial wall of secondary xylem tracheids; F, slide MN864-C1, detail of the cortex in transverse section showing a decrease in cell size and increase in wall thickness towards the periphery of the axis; G, slide MN864-A5, longitudinal section showing elongated cells of the cortex; H, slide MN864-A5, longitudinal section at a node showing the cortex (C) and a leaf base (l) cut obliquely; I, slide MN864-A5, detail of the leaf base on H; J, slide MN864-A6, longitudinal section at a node showing the cortex (C) and a leaf (l) showing its length and thickness. Scale bars: A, H, J, 500 µm; B, I, 200 µm; C, E-G, 50 µm; D, 250 µm.