This species was found in Jurassic rocks in the Otago district of New Zealand in association with _Cladophlebis denticulata_[785] (fig. 257). The type-specimen forms part of a stem 17 mm. in diameter surrounded by a broad mass of crowded leaf-bases. The stele consists of an almost continuous xylem ring (fig. 252) enclosing a wide pith: the phloem and inner cortex are not preserved but the peripheral region of the stem is occupied by a sclerotic outer cortex. The mass of encasing leaf-bases resolves itself on closer inspection into zones of foliage-leaf petioles and the petioles of scale-leaves with an aborted lamina. A similar association of two forms of leaf is seen in the existing American species _Osmunda Claytoniana_ and _O. cinnamomea_. The cortex and armour of leaf-bases are penetrated by numerous diarch roots. The xylem cylinder, six to seven tracheae broad, is characterised by the narrower diameter of its innermost elements and—an important point—by the fact that the detachment of a leaf-trace does not break the continuity of the xylem cylinder (fig. 252). Each leaf-trace is at first elliptical in section; it then becomes curved inwards and gradually assumes the horse-shoe form as in _Zalesskya_ and in the recent species. The single endarch protoxylem becomes subdivided until in the petiole it is represented by 20 or more strands. [Illustration: FIG. 252. _Osmundites Dunlopi_ Kidst. and G.-V. Portion of xylem showing the departure of a leaf-trace. (After Kidston and Gwynne-Vaughan; × 36.)] In the continuity of the xylem cylinder this species of _Osmundites_ shows a closer approach to _Todea barbara_ or _T. superba_ (fig. 221, B) than to species of _Osmunda_; it differs from _Zalesskya_ in having reached a further stage in the reduction of a solid protostele to one composed of a xylem cylinder enclosing a pith. This difference is of the same kind as that which distinguishes the stele of _Lepidodendron rhodumnense_ from _L. Harcourtii_. In _Lepidodendron_ short tracheae occasionally occur on the inner edge of the xylem cylinder, and in recent species of _Todea_ the same kind of reduced tracheae are met with on the inner edge of the xylem[786]. In both cases the short tracheae are probably vestiges of an axial strand of conducting elements which in the course of evolution have been converted into parenchymatous cells. In _Lepidodendron vasculare_ the mixed parenchyma and short tracheae in the centre of the stele represent an intermediate stage in xylem reduction, and the arrangement in vertical rows of the medullary parenchyma in _Lepidodendron_ is precisely similar to that described by Kidston and Gwynne-Vaughan in _Thamnopteris_. In both cases the rows of superposed short cells have probably been produced by the transverse septation of cells which began by elongating as if to form conducting tubes and ended by assuming the form of vertical series of parenchymatous elements.