FIG. 6 in Anatomy, affinities, and evolutionary implications of new silicified stems of Sphenophyllum Brongniart, 1828 from the early Carboniferous (Mississippian) of France and Germany

FIG. 6. — Specimens with secondary growth from Kahlleite, Germany (KLC4 & KLC3): A, B, slides KLC4-A1 and KLC4-B1, general view of KLC4 in transverse sections at two different levels showing the triangular stele with three strands of protoxylem (arrows) and the outer cortex with 7 (A) or 6 (B) ridges; C, slide KLC4-B1, detail of the protostele in KLC 4 in transverse section showing a lacuna in at least one of the protoxylem locations; D, slide KLC4-B1, detail of the primary (X1) and secondary (X2) xylem in KLC4; note the files of secondary xylem tracheids separated by rays (arrows); E, slide KLC4-B1, detail of the outer cortex showing a decrease in cell diameter towards the outside of the stem (top of the image); F, slide KLC3-C, centre of KLC3 in a region where the center is preserved; arrows indicate the tip of the three arms of the actinostele; G, slide KLC3-C, detail of the protostele of KLC3 showing a primary xylem pole (arrow) and the development of secondary xylem (X2) around the primary xylem (X1); H, slide KLC3-C, detail of the secondary xylem in KLC 3 showing tracheids and rays (arrows) in transverse section. Scale bars: A, B, 500 µm; C, 200 µm; D, H, 50 µm; E, 20 µm; F, 250 µm; G, 100 µm.