The secondary xylem shows incomplete rings or arcs of narrower elements, which at first sight give the impression of annual rings: the occurrence of similar incomplete or pseudo-rings is a common feature in _Lepidodendron_ and other Palaeozoic stems. The secondary tracheids (54·4μ in tangential diameter, 68·5μ in radial diameter) have usually a single series of broadly oval bordered pits on the radial walls with here and there two rows (fig. 462, D). In one case only were the pits of the medullary rays recognised (fig. 462, F). The rays are uniseriate, generally 1–2 cells deep, but occasionally 3 cells in depth and very rarely deeper. The cambium is of the normal type, and in some specimens secondary phloem was found consisting of bands, 4–5 layers broad, of stone-cells alternating with tubular thin-walled elements, presumably sieve-tubes. [Illustration: Fig. 462. _Protopitys Buchiana_. A, B. Central region of the stem showing the pith, the primary xylem (black in fig. A) and (A) the inner part of the secondary xylem; _a_, shoulders of xylem at the leaf-gaps; _lt_ leaf-trace; _px_ protoxylem. C. Secondary, _x_², and primary xylem, _x_¹. D. Radial longitudinal section of the secondary xylem. E. Scalariform tracheid of the primary xylem. F. Pits on the medullary-ray cells. (After Solms-Laubach.)] As Solms-Laubach says, it is highly probable that each leaf-trace, which forks close to its exit from the primary xylem, became further subdivided before reaching the leaf. Morphologically, _Protopitys_ is of special importance as a type possessing characters that indicate a connexion with Conifers or Cordaitean genera, notably the structure of the secondary wood, while the presence of foliar gaps is a feature reminiscent of Ferns. The primary xylem resembles that of some of the Palaeozoic arborescent Lycopodiales, but in _Protopitys_ the interruptions in this tissue are due to the emission of leaf-bundles, whereas in the discontinuous primary xylem of some Sigillarias[533] the gaps have no connexion with leaf-traces. Moreover the distichous leaves of _Protopitys_ and the larger, branched, leaf-traces are other distinguishing features. The pitting of the primary xylem is like that in the Lycopodiales and Filicales, while that of the secondary wood shows a closer approach to the coniferous type. A comparison may also be made with the transversely elongated pits of _Cladoxylon Kidstoni_[534]. A piece of wood agreeing anatomically with the Silesian species of _Protopitys_ has been found in the Yoredale rocks of England[535].