This species is represented by some large trunks, in some cases with a diameter of 40 cm., discovered by Mr Kay in the Coal Measures of Worcestershire[686]. The pith is very small and shows no indication of a discoid structure, but owing to its poor preservation no sections could be obtained of this region. The secondary wood is characterised by the large number of uniseriate medullary rays 1–27 cells in depth; the tracheids have usually two or sometimes three rows of alternate and contiguous bordered pits on the radial walls. Arber regards the absence of a discoid pith as a fatal objection to a reference of the stems to _Cordaites_ and speaks of them as affording further evidence of the occurrence of Coniferae in the higher Coal Measures of the Midlands. It is, however, impossible to determine the position of the species in the absence of any data with regard to the structure of the perimedullary region, and without such information we are hardly justified in regarding _Dadoxylon Kayi_ as a member of the Coniferales. [Illustration: Fig. 474. _Dadoxylon materiarum._ Transverse (A) and tangential (B) sections of the secondary xylem. (Kidston Coll. 222, 224.)] [Illustration: Fig. 475. _Dadoxylon materiarum._ A–C radial longitudinal sections of the secondary xylem. (Kidston Coll. 225.)] _Dadoxylon Pedroi_ Zeiller. This species from Upper Carboniferous or possibly Lower Permian strata in Brazil[687] has a pith 3·8 cm. in diameter composed of parenchyma with scattered secretory sacs and characterised by the occurrence of three equidistant bays projecting into the cylinder of wood (fig. 476, A) which extend through the length of the specimen (6 cm.): these, as Zeiller suggests, may be connected with the departure of leaf-traces or branches. The xylem is entirely composed of centrifugal elements and shows a broad transitional zone (fig. 476, B) including spiral, scalariform, and reticulate tracheids, but the bordered pits are less numerous and less crowded than in many species of _Dadoxylon_. The rays are 1–2 cells broad and reach a depth of 50 cells. The most striking features are the solid and not discoid pith with its three rounded bays and secretory canals, also the smaller number and frequently circular form of the pits on the tracheids. Zeiller considers that the stem is that of some Cordaitean plant though probably not a true _Cordaites_. White[688] questions the advisability of adopting the generic name _Dadoxylon_ and suggests the possibility, though without any satisfactory evidence, that it is the stem of a _Gangamopteris_. Failing further information, there would seem to be no sufficient reason for the institution of a distinctive generic name. [Illustration: Fig. 476. _Dadoxylon Pedroi._ A, transverse section showing the pith and part of the secondary wood. B, longitudinal section of part of the secondary wood. (After Zeiller.)] _Dadoxylon permiense_ (Renault).