Part of a transverse section of a cylindrical stem is represented diagrammatically in fig. 416, D. Very little of the cortex is preserved: a parenchymatous axial region with scattered secretory canals contains four oval or cylindrical vascular steles, the stellate columns of Cotta or star-rings of later authors. These are of the same nature as the small central stele in the English _Medullosa centrofilis_. The central region of the stem in this specimen is completely surrounded by a narrow cylinder of inversely orientated secondary xylem and phloem (fig. 416, D), the phloem being on the inner side of the xylem. Beyond the xylem is a parenchymatous band containing scattered groups of primary xylem tracheids with spiral, scalariform, and reticulate pitting, and this zone, which is usually designated the ‘partial pith,’ is succeeded by a second and broader, normally orientated, cylinder of secondary xylem and phloem. In this section the two concentric cylinders separated by the partial pith form a solenostele like that of several recent Ferns except in the presence of secondary tissue. The term ‘partial pith’ applied to the tissue between the two cylinders of secondary tissue is misleading: this tissue (fig. 416, D, _p_) is the primary xylem of the stele and is homologous with the primary portion of the stele of _Heterangium_ and of the steles of _M. anglica_. In many sections the continuity of the tubular stele is broken. In a section in the British Museum cut from one of Cotta’s specimens[260], 6 × 3·5 cm. in diameter to the outer edge of the vascular tissue, the cylindrical stele is interrupted at two places. An example of the interrupted type of stele is shown in fig. 416, F, and in fig. 416, H: the latter belongs to a distinct species. The complete type of cylindrical stele is exceptional and occurs occasionally at different levels in the stem. An important point is that the frequent breaks in the cylinder are not connected with the exit of leaf-traces and do not, therefore, correspond to the foliar gaps in the solenostele or dictyostele of a Fern. The secondary xylem is of the cycadean type (fig. 418, B, D) like that of _Heterangium_ and _Lyginopteris_ and several other stems. Each of the star-rings in the axial region consists of a parenchymatous core with scattered primary tracheids enclosed by secondary vascular tissue (fig. 418, B). The star-ring shown in fig. 418, B, from a Chemnitz stem illustrates the characteristic cycadean character of the secondary xylem with broad medullary rays: some of the innermost elements are in contact with the primary tracheids. The phloem is rendered conspicuous by the black contents in some of the elements. Both the star-rings and the larger peripheral steles are constructed on the same plan and agree with the steles of _M. anglica_. The star-rings occasionally branch and anastomose with one another and with the encircling stele. The star-ring in fig. 416, D at _a_ is about to give off a small strand.