Cordaixylon sp. (Fig. 9A)

We illustrate a small, partly decorticated stem, about 6 mm in diameter. The cylinder of secondary xylem averages 4 mm and the pith 1.5 mm in diameter.The wood tracheids are small, ranging from 12-15 µm in diameter for the innermost ones to 20-30 µm in diameter at the periphery.The endarch maturation of the primary xylem conforms to the genus Cordaixylon Grand’Eury. On the surfaces studied the pith is solid and consists of a parenchyma of small cells (around 30 µm in diameter).One incomplete rachis, crescentshaped in cross section (P, Fig.9A), is closely associated with the stem; it certainly represents one petiole of this plant, as suggested by its vascular anatomy consisting of more than six bundles as it should be expected in the petiole of such a young cordaitean stem. Associated in the same chert block we found fragments of leaves with a thin lamina (Fig. 9F, see below).

E

doxylon cf. rollei Unger, isolated wood fragment; A, transverse

section showing the distorted files of tracheids (SAR07BB03);

B, detail of the same showing rows of tracheids separated by narrow rays; C, radial longitudinal section showing poorly preserved uni-to biseriate circular pits of tracheids between two rays (SAR07BLR01); D, tangential longitudinal section showing the narrow (uniseriate) rays of variable height (SAR07AL07); E, isolated wood of pteridosperm affinities, radial longitudinal section showing the broad tracheids with multi (4 to 5)-seriate pitting (SARBB02). Scale bars: A, 1 mm; B, 0.5 mm; C-E, 100 μm.

Cordaites leaves

Some rock specimens contain diverse cordaitean leaves interspersed among leaves of other plants (Fig. 9B). These leaves, of different thickness and anatomy,are illustrated at the same magnification on Figure 9 C-F.