The diagrammatic sketch shown in fig. 179, A, was made from a section figured by Williamson in 1893[349]; it has a diameter of 9 × 8·5 cm. The stele is of the medullated type like that of _L. Wünschianum_, and the outer edge of the primary xylem is characterised by sharp and prominent projecting ridges similar to those of _L. fuliginosum_ but rather more prominent. Parenchymatous cells succeed the xylem, as in other species, but in this case there is no indication of meristematic activity; beyond this region occur occasional patches of a partially destroyed secretory zone. Remains of a lacunar tissue are seen in the middle cortical region; also numerous leaf-traces, _lt_, consisting of a tangentially elongated xylem strand accompanied by a strand of secretory zone tissue enclosed in a sheath of delicate parenchyma. In the inner part of the outer cortex, _c_³, the leaf-traces lie in a space originally occupied by the parichnos; in the outer portion of the same region a band of secondary cortex, _pd_, has been formed; immediately internal to this occur numerous patches of secretory tissue, represented by small dots in the drawing close to _pd_; one is shown on a larger scale in fig. B. The position of the phellogen is seen at _a_; external to this are radial rows of rather large cells with dark contents. [Illustration: FIG. 179. A–D. _Lepidodendron Harcourtii_, Witham. E. _Lepidodendron fuliginosum_, Shore, Lancashire. A, B. From a specimen in the Williamson Collection, British Museum (No. 380), from Airdrie, Scotland. C, D. From sections in the Collection of Dr Kidston, from Shore, Lancashire.]