Prof. Zeiller[501] retains the older name _Ulodendron minus_ Lind. and Hutt. in place of König’s specific designation and dissents from Kidston’s identification of _Ulodendron minus_ and _U. majus_ of Lindley and Hutton as one species; he is also inclined to refer these Ulodendron axes to _Lepidodendron_. In spite of the superficial resemblance to _Sigillaria_ of the specimens described by Kidston, and which I have had an opportunity of examining, I venture to regard their reference to that genus as by no means definitely established. We must recognise the difficulty in certain cases of drawing any satisfactory distinction between _Sigillaria_ and _Lepidodendron_ based on external features, and while giving due weight to the conclusions of so experienced a palaeobotanist as my friend Dr Kidston, I venture to think we are not in a position to state with confidence that _Sigillaria_ possessed Ulodendron shoots. ii. _Leaves._ The leaves of _Sigillaria_ agree closely with those of _Lepidodendron_; they are either acicular (fig. 200, D) like Pine needles or broader and flatter like the leaves of _Podocarpus_. Their attachment to comparatively thick branches[502] shows that they persisted, in some cases at least, for several years as in _Araucaria imbricata_. The lower surface of the lamina was characterised by a prominent keel (fig. 142, A and C) which dies out towards the apex; on either side of it are well-defined stomatal grooves (figs. 142, _g_, _g_; 143, A; 200, D, _g_). The upper face may be characterised by another groove (fig. 142, B) but without stomata. The occurrence of the stomatal grooves, the abundance of transfusion tracheae (fig. 142, _t_) surrounding the vascular bundle, and the presence of strengthening hypodermal tissue suggest that the leaves of _Sigillaria_ were of a more or less pronounced xerophilous type and had a fairly strong and leathery lamina. The mesophyll tissue consists either of short parenchymatous cells or of radially elongated palisade-like elements and has the loose or lacunar arrangement characteristic of the aerating system in recent leaves; the slight development or absence of palisade-tissue may indicate exposure to diffuse light of no great intensity. In most species there is a single vein, but in others the xylem forms a double strand (fig. 142, B). Sections of the lamina near the apical region present a more circular form, owing to the gradual obliteration of the upper groove and lower keel and to the dying out of the stomatal grooves.