Fig. 179, C, _x_, shows the characteristic form of the primary xylem edge, beyond which are seen oval or circular leaf-traces with a mesarch protoxylem, _lt_, _px_. It is possible that this specimen may not be specifically identical with Witham’s species, but it represents a very similar if not identical type; it may on the other hand be referable to _L. fuliginosum_. The importance of the specimen, apart from its precise specific position, is that it serves to illustrate the general appearance of the xylem surface met with in both species, _L. Harcourtii_ and _L. fuliginosum_. A tangential longitudinal section, taken through the line _ab_ in fig. C, is represented in fig. 179, D. The xylem of the leaf-traces _lt_, consisting chiefly of scalariform tracheae, alternates with patches of crushed and delicate parenchyma which immediately abut on the primary xylem; at _p_, _p_, the section passes through some of the projecting arms of the xylem cylinder; at _m_ is seen a patch of meristematic zone tissue. This section together with the similar section of _Lepidodendron vasculare_ described on a previous page demonstrates that the projecting ridges of the primary xylem form apparently vertical bands: they are not characterised by a lattice-work arrangement as described by Bertrand and by other authors who have accepted his conclusions. If a reticulum of intersecting ridges were present on the face of the xylem cylinder its existence would be revealed by such a section as that represented in fig. 179, D. [Illustration: FIG. 180. _Lepidodendron Wünschianum._ From Arran. (⅕ nat. size.) (Sedgwick Museum, Cambridge.)] 6. _Lepidodendron Wünschianum_ (Williamson). Figs. 180–184.