A type of _Stigmaria_ characterised by centripetal primary wood has been described by Weiss[597] and referred by him to _Bothrodendron mundum_; the main results of his observations are stated in the account of _Bothrodendron_ on a subsequent page. This discovery is of considerable interest not only as rendering our knowledge of _Bothrodendron_ remarkably complete but as confirmatory of Renault’s account of French Stigmarian axes in which centripetal primary wood is well developed between the secondary xylem and the centre of the stele. The Stigmarian axis of Bothrodendron was originally figured by Williamson as _Lepidodendron mundum_[598]. The chief difference between Weiss’s specimen and those described by Renault[599] as the Stigmarian axes of _Sigillaria Brardi_, is that in the English plant the centripetal wood forms a cylinder of uniform breadth instead of a band with a crenulated inner margin as figured by Renault. [Sidenote: STIGMARIA] [Illustration: FIG. 210. _Stigmaria._ A. Transverse section of vascular bundle of rootlet and part of outer cortex. _t_, tracheae. (After F. E. Weiss.) B, C. Vascular bundle of rootlet; in C a series of small tracheae are shown extending from the protoxylem. D. Rootlets from the outer cortex of E. E. Part of a large _Stigmaria_: _St_, stele; _s_, intruded rootlet. F. Vascular bundle and tracheae passing obliquely towards the outer cortex, _c_³. G. Outer cortex of _Stigmaria_. H. Diagrammatic section of _Stigmaria_: _p_, phelloderm; _r_, rootlets.] An interesting agreement between the French and English specimens is the occurrence in the cortex of groups of reticulate elements: in Weiss’s section these are short and wide and occur in the middle cortex; in Renault’s plant they are more fusiform and occur in the secondary cortical tissue. These elements appear to have been arranged as an interlacing network in the middle cortex and were in close connexion with the rootlet-bundles, comparable, as Weiss points out, with the transfusion tracheids accompanying Lepidodendron leaf-traces. It is probable that these short and wide tracheal elements served for water-storage and thus afford another indication of the xerophilous character of the Carboniferous Lycopods, a feature possibly connected with a salt-marsh habitat.