The type-specimen, reproduced natural size in fig. 446, A, B, consists of a fragment of stem which at first sight bears a close resemblance to _Cordaites_, but the apparent pith, 1·9 cm. in diameter, is the primary xylem of the stele and is enclosed by an incomplete cylinder of secondary xylem 2 cm. broad. The distinction between the lighter primary xylem and the darker secondary cylinder is especially well marked in the longitudinal section (fig. 446, B). The central region, shown on a larger scale in fig. 447, is occupied by groups of tracheids varying in size and shape associated with thin-walled parenchyma: the latter is represented by lighter patches in the section. The majority of the tracheids are characterised by their great breadth—in some cases ·4 mm.—and their isodiametric or even horizontally elongated and flattened form. Some of these large metaxylem elements are seen in longitudinal section at _m_ in fig. 448 where the shrinkage and partial decay of the parenchymatous tissue have resulted in the separation of transverse bands of xylem simulating the discoid pith of a _Cordaites_. The walls of these tracheal cells are covered with multiseriate pits. With the short and sometimes flattened xylem elements occur others of greater length, but these are chiefly met with in the more peripheral part of the central region where some of the tracheids are much narrower and have the form of ordinary water-conducting elements. On one side of the primary xylem in fig. 447 an oval and more compact group of narrow and longer tracheids is seen at _lt¹_; this is a leaf-trace about to enter the secondary-xylem cylinder on its outward course. The same leaf-trace is shown at _lt_ in fig. 446, B; as it descends the trace becomes less distinct and its elongated elements gradually merge into the general mass of metaxylem. A portion of this leaf-trace is seen in fig. 448, B, _lt_, close to the inner edge of the secondary xylem, _x²_, and abutting internally on the contracted tissue, _m_, which consists mainly of large and short tracheae with remains of associated parenchyma. The trace includes some conjunctive parenchyma interspersed with the tracheids: on its outer surface, that is on the abaxial edge of the ovate xylem strand as shown at _lt¹_ in fig. 447, there are six external protoxylem strands. In the peripheral region of the primary xylem of the section reproduced in fig. 447 there are several more or less well-defined leaf-traces, _e.g._ _lt²_, _lt³_; these differ from that seen at _lt¹_ in their greater tangential breadth and in the less compact arrangement of the tracheids. As each trace is followed downwards in the primary region of the stele it tends to become broader, especially in a tangential direction; the spiral protoxylem strands are more widely separated (fig. 448, A, _px_) and the elongated and comparatively narrow tracheids as they spread out fan-wise are reduced in length, finally passing over into the broad