The axis of the strobilus has a stele characterised by a pith of elongated elements, most of which have thin walls; the xylem cylinder possesses about twenty protoxylem strands forming more or less prominent exarch ridges. The cortex exhibits a differentiation comparable with that in the shoots of _Lepidodendron_. The sporophylls are arranged in alternating verticils, each whorl consisting of ten members: the narrow horizontal pedicel of a sporophyll, containing a single vascular bundle, as shown in fig. 192, is expanded distally into a prominent upper lobe bearing a cushion of small and delicate cells, to which the sporangium is attached, and prolonged obliquely upwards as a free leaf-like lamina. The lower blunt prolongation of the sporophylls appears to form a thick dorsal lobe, but, as Lang has pointed out, it is highly probable that the present form of the dorsal lobe is of secondary origin, and is “due to the disappearance of a mucilage cavity from a large sporophyll base[444].” As Miss Berridge remarks, the vascular bundle of the sporophyll does not give off a branch to the ventral lobe and sporangium. In attachment, in shape, and in the structure of the wall the sporangia differ markedly from those of _Lepidostrobi_. The spores, which also constitute a characteristic feature of the genus, have a maximum diameter of 0·14 mm.; they are described as oblate spheroids with a broad hollow wing running round the equator (fig. 192) comparable with the air-sacs of the pollen of _Pinus_. Scott points out that the spores of _Spencerites_ are intermediate in size between the microspores of _Lepidodendron_ and the megaspores of _Lycopodium_; it is difficult therefore to decide to which category they should be referred. _Spencerites_ is clearly distinct from _Lepidostrobus_; the absence of a ligule, the manner of attachment of the sporangia, and the form and size of the spores, are characteristic features. A comparison of _Spencerites_ with the strobili of _Lycopodium cernuum_ (figs. 123, 126–129) has recently been made by Lang, who draws attention to the striking agreement as regards general plan and even detailed structural features between the Palaeozoic and the recent type of strobilus. It is interesting to find, as Lang points out, that in the original account of the fossil cone by Williamson, the view is expressed that the sporangiophores were confluent. An examination of the section figured by Williamson[445] led Lang to confirm this opinion. It would be out of place to enter here into a detailed comparison of _Spencerites insignis_ and the cone of _Lycopodium_, but the resemblances are considered by Lang to be sufficiently close to suggest that the striking similarity may be indicative of relationship[446].