IV. Contributions to the knowledge of lower carboniferous plants. I.—On the genus Rhacopteris, Schimper . II.—On the morphology of Sphenopteris Teiliana, Kidston, and its bearing on the position of the fructification on the frond of some lower carbon­iferous plants

Abstract
The genus Rhacopteris was instituted by Schimper in 1869 for a type of fern-like frond of Carboniferous Age. It included one species Rhacopteris elegans , Ettingshausen sp. In 1879 the conception of the genus was extended and the following species were included: Rhacopteris inæguilatera and R. petiolata , Göppert spp., R. paniculifera and R. transitionis , Stur spp., R. speciosa , Ett., and Rhacopteris sp . Gomes. The Upper Carboniferous representatives differ in some respects from those of the Lower Carboniferous, and Oberste-Brink suggests a subdivision of the genus into Eurhacopteris and Anisopteris ; Eurhacopteris , including the Upper Carboniferous forms, R. elegans , Ett. sp., R. asplenites , Gutbier sp., R. dubia , Lindley and Hutton sp., R. Busseana , Stur, and R. Moyseyi , Arber; Anisopteris , including all the Lower Carboniferous forms. Oberste-Brink regards this as a more natural grouping of the constituents of Rhacopteris , Schimper, considering, moreover, that it receives support from the fact that this division of the genus corresponds to a stratigraphical separation of no small order. Oberste-Brink states that no Rhacopterids have been recorded from strata lying between the Middle Productive (Westphalian Series, Upper Carboniferous) Measures and the Culm (Lower Carboniferous). Since it is doubtful whether the division of the genus he suggests is a natural one, and not one with a stratigraphical bias, it seems on the whole inadvisable to adopt this nomenclature. The term Rhacopteris is of such widespread use among authors for these Lower Carboniferous fronds that it would merely increase the synonymy without any obvious advantage from the point of view of the systematist. We are concerned only with the Lower Carboniferous species in this communication. The fern-like fronds of Rhacopteris are characteristically pinnate, linear, and contracted towards the base. The pinnules are opposite or alternate, often asymmetric, contracted at the base, entire or divided into lobes, each of which has one or more veins. The texture of the lamina in many of the species was probably coriaceous. No midrib is present in the pinnule, but in some species by a series of unilateral dichotomies a one-sided arrangement results, from which it appears that a main vein passing along the lower margin of the pinnule gives rise to a series of more or less equal veins, which traverse the lamina to the upper margin, dichotomising one or more times on the way. No anastomoses have been observed between the veins.

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