[Illustration: FIG. 172. _Lepidodendron fuliginosum._ From a section (4 × 3·4 cm.) in the Williamson Collection, British Museum (No. 379), figured by Williamson, _Phil. Trans. R. Soc._ =1881=, Pl. 52.] The secretory zone of _Lepidodendron fuliginosum_ agrees essentially with that of other species; it usually presents the appearance shown in fig. 168, B, _sc_; fig. 169, B and C; fig. 170, B (longitudinal section); fig. 171, D, _sc_. The comparatively large clear spaces which characterise this tissue, as seen in fig. 168, B, appear to owe their origin to groups of small cells which gradually break down and give rise to spaces containing remnants of the disorganised elements, as in fig. 171, D, and fig. 169, B, _b_. The secretory tissue seen in fig. 170, B, consists of large and small parenchymatous cells without any of the broad sacs or spaces such as are shown in fig. 169, C. Fig. 172 represents a diagrammatic sketch of a transverse section (4 × 3·4 cm. in diameter) of a young shoot from the Lower Coal-Measures of Lancashire figured by Williamson[327] in 1881 as _Lepidodendron Harcourtii_. It shows the features characteristic of _L. fuliginosum_ and is of importance as affording an example of a shoot giving off a branch from the stele to supply a lateral axis of the type characteristic of _Halonia_. The exit of the branch-stele forms a gap in the main stele; a ramular gap as distinguished from a foliar gap. The outgoing vascular strand is at first crescentic, but becomes gradually converted into a solid stele. The primary xylem of the main stele (black in the figure) consists of a ring six tracheae in breadth; this is succeeded by a few layers of dark parenchymatous cells and a band of radially elongated elements, _a_, which abuts on the secretory zone. The middle lacunar cortex, _c_², with _Stigmaria_ rootlets, _s_, is fairly well preserved. In the outer cortex occur several leaf-traces, _lt_, accompanied by spaces originally occupied by the parichnos strand, _p_. A band of secondary cortex, consisting chiefly of phelloderm, is seen at _pd_. The prominent leaf-cushions, some of which show the parichnos, _p_, appear to be of the Lepidophloios type. • • • • • It remains to consider the external characters of Lepidodendroid shoots possessing the anatomical features represented by the comprehensive species _Lepidodendron fuliginosum_.