In a note published in 1907, Kidston[508] demonstrated the association of _Sigillariopsis_ leaves with an undoubted Sigillarian stem of the Rhytidolepis type and expressed his conviction that Renault’s genus is identical with _Sigillaria_. The correctness of Kidston’s conclusion has been proved by Arber and Thomas[509] who found that the leaf-traces of _Sigillaria scutellata_ bifurcate during their course through the outer region of the cortex and enter the leaf as two distinct strands of primary xylem. In the section from Dr Kidston’s collection shown in fig. 142, B, the lamina, 4 mm. wide, consists mainly of thin-walled assimilating tissue composed of radially elongated cells abutting at the periphery on hypodermal mechanical tissue, except at the edges of the stomatal grooves which are bounded by the small-celled epidermis. A broad sheath of thicker-walled elements, _s_, surrounds numerous scattered transfusion tracheae, _t_, and below the two xylem strands, _x_, which are embedded in delicate parenchyma there is a crescentic band of dark tissue, _a_, resembling the smaller strand, _a_, in fig. 142, A′, and the secretory zone tissue of a Lepidodendron stem. iii. _Fertile shoots of_ Sigillaria. Reference has already been made to the manner of occurrence of strobili on Sigillarian stems; it remains to describe the structure of these reproductive shoots. _Sigillariostrobus_, the name given to Sigillarian strobili, may be defined in general terms as follows: Cylindrical cones, rarely dichotomously branched[510] as in species of _Lycopodium_ and _Selaginella_, which may reach a length of 30 cm. (_e.g._ _Sigillariostrobus nobilis_ Zeill.[511]) and a diameter 2–5 cm.; peduncle long and slender, sometimes bearing acicular bracts or, after leaf-fall, characterised by leaf-cushions and leaf-scars like those on vegetative shoots (fig. 201, E). The stalked cones are borne in irregular verticils and in some species in vertical series, the fertile zones being separated by comparatively long sterile portions of the stem (fig. 199). The cones were deciduous and, in certain cases if not in all, the individual sporophylls became detached from the cone-axis on maturity. The slender axis bore spiral or verticillate imbricate sporophylls attached at right angles or more or less obliquely. The basal rhomboidal portion bore spores on its upper surface (fig. 201, F), presumably enclosed in a somewhat radially elongated sporangium (fig. B) and was prolonged distally into a narrow lanceolate free portion, in some species with a ciliate border (fig. D). The sporangia probably produced megaspores and microspores, but such spores as have been recognised appear to belong to the former category. The designation _Triletes_ is applied to isolated spores of _Sigillaria_ or to those of _Lepidodendron_.