FIG. 4 in Anatomy, affinities, and evolutionary implications of new silicified stems of Sphenophyllum Brongniart, 1828 from the early Carboniferous (Mississippian) of France and Germany

FIG. 4. — Specimen from Coumiac,Montagne Noire, France (MN911):A, slide MN911-A1,general view of the specimen above the level of branching,showing a main axis (a) on the left with a trace to a leaf (l) and a smaller axis (b) on the right;this section corresponds to the level 7 on Figure 7; B, slide MN911-A1,general view of the main axis in transverse section showing the cortex with six lobes and triangular primary xylem (arrows); C, slide MN911-A1,detail of the stele on A; note the presence of lacunae (arrow) at the extremity of each arm of the stele and the lack of secondary vascular tissues;D, slide MN911-A2,pitting on the primary xylem of an outgoing branch trace;E, slide MN911-A2, general view of the smaller axis shown on A; note smaller size of the primary xylem compared to B; F, slide MN911-A2,detail of the largest axis showing outgoing paired vascular traces at the extremity of the arm; G, slide MN911-A2, detail of F showing the protoxylem strand (arrow) and two outgoing traces (lt); H-K, successive sections showing the branching of the axis; H, below the division; I, node with leaves; J, branching; K, branching complete. These photos correspond to the levels 1, 2, 4, and 5 on Figure 7 and to polished surfaces MN911-B1i, MN911-B1s, MN911-B2s, and MN911-B3i. Scale bars: A, H-K, 1 mm; B, E, F, 200 µm; C, 80 µm; D, 50 µm.