by Salisbury[811] to the occurrence of bilaterally and radially symmetrical fruits among British Carices and to a similar mixture in the family Polygonaceae. The acquisition of more detailed and accurate knowledge of Palaeozoic seeds led to an extension of the two-fold division of Brongniart and Oliver which is based on such characters as the position of the vascular tissue in relation to the integument and nucellus, the form of the pollen-chamber, and other features. The division Lagenostomales has been instituted for _Lagenostoma_ and some other Radiosperms connected by certain important characters: these seeds may be referred to the Pteridospermeae though it is only in the case of _Lagenostoma_, and to a less extent _Sphaerostoma_, that a correlation between vegetative organs and seeds has been rendered sufficiently probable to justify an assumption of generic identity. The name Trigonocarpeae[812] has recently been used for a section of Radiosperms represented by _Trigonocarpus_, _Stephanospermum_, and other genera. Although the genus _Stephanospermum_, as Oliver[813] says, may be regarded as the type-genus of a group of seeds, it is more fitting, as the same author[814] insists, to adopt a divisional term based on the generic name of the much more widely spread and more familiar _Trigonocarpus_. For the sake of uniformity in nomenclature it is proposed to adopt the name Trigonocarpales instead of Trigonocarpeae to rank with Lagenostomales. The Platyspermeae comprise such seeds as _Cardiocarpus_, _Mitrospermum_, and _Rhabdospermum_, genera characterised by well-marked anatomical features and probably Cordaitean; it has, however, been shown that typical Platysperms were also borne on leaves of Pteridosperms and, as Mrs Arber[815] says, the notion that every member of the Platyspermeae was necessarily a Cordaitean seed has been discredited by the discovery of the seeds of _Aneimites_ (_Wardia_) and _Pecopteris Pluckeneti_[816]. For general purposes it is hardly necessary to adopt the subdivisions of the Lagenostomales used by Oliver and Salisbury[817], though as facts accumulate we shall no doubt be able to make further advances towards a natural system of classification. The following three divisions of Permo-Carboniferous seeds include genera founded on petrified specimens and thus afford valuable morphological data. The groups Lagenostomales and Trigonocarpales include types belonging to closely related plants, a relationship clearly expressed in the seed-characters. I. +Lagenostomales.+