The French species _Heterangium Duchartrei_[229] Ren. from Permian rocks was originally referred by Renault to the genus _Poroxylon_: it is represented by little more than the xylem of the stele and bears a close resemblance to _H. tiliaeoides_. _Heterangium punctatum_ Ren. and _H. Renaulti_[230] (Brongn.) also from the Permian of France were originally placed in the genus _Lycopodium_ and afterwards recognised as stems of _Heterangium_. A fourth French Permian species, _H. bibractense_[231], is peculiar in the possession of a very small primary stele encircled by deep wedges of secondary xylem, but without more information it is impossible to speak with confidence as to its systematic position. Kubart[232] has recently published brief descriptions of some stems from the Ostrauer coal-basin in Moravia all of which he regards as specifically distinct from the English types. In _Heterangium Sturi_ the primary xylem is almost exarch and the peripheral xylem groups are not very clearly defined: in _H. alatum_, so called from the presence of lateral wings on the petioles, the leaf-trace strands are more sharply differentiated from the rest of the stele. _H. polystichum_ is a similar type, and _H. Andrei_, with a relatively larger amount of parenchyma in the stele and thicker stems forms an additional link between _Heterangium_ and _Lyginopteris_[233]. Prof. Johnson[234] has described a species of _Heterangium_, _H. hibernicum_, from Upper Devonian and Lower Carboniferous beds in Co. Cork, Ireland, based on some impressions of frond fragments without any pinnules. The occurrence of numerous transverse striae on the rachis and lateral branches suggests comparison with _Heterangium_ fronds, but an examination of the specimens led me to suspect that some at least of the striae are cracks and not original features. The presence of spur-like appendages from the lower surface of the pinnae near their origin from the rachis is recorded as a peculiar character, and some obscure oval bodies, the nature of which is extremely doubtful, are considered to be seeds. The imperfection of the material hardly justifies the institution of a new species of _Heterangium_. _Heterangium_ ranges from the Lower Carboniferous to the Permian strata and is thus older than _Lyginopteris_ which in the form of petrified stems is not recorded from the Lower beds of the Carboniferous system. _Heterangium_ has been described as having a ‘great preponderance of fern-like characters,’ but having regard to the resemblance of the primary xylem of the latter to that of the Osmundaceae it would seem doubtful whether in their relation to the Ferns there is any important difference. _Heterangium_ may safely be spoken of as the more primitive genus. The polydesmic character of the petioles of most species is particularly interesting as it brings the genus nearer to the Medulloseae and to _Rhetinangium_[235]. CHAPTER XXX.