_Psaronius coalescens_[1077] (fig. 296, C) illustrates a somewhat different arrangement of vascular tissue which approaches more closely to the polycyclic structure characteristic of such recent ferns as _Matonia_ and _Saccoloma_. A still closer resemblance to the solenostelic type is seen in _Psaronius Renaulti_ from the Lower Coal-Measures of England which Scott[1078] describes as characterised by a single annular stele, interrupted only by the exit of leaf-traces. As he points out, it is noteworthy that this species is distinguished by the simplest form of stele met with in the genus; it is the oldest species and may be regarded as the most primitive representative of the genus _Psaronius_ so far discovered. [Illustration: FIG. 298. A. _Caulopteris peltigera_. B. _Megaphyton insigne_. (After Grand’Eury.) Much reduced.] _Psaronius stems preserved as casts showing surface-features, or in a decorticated state._ i. _Caulopteris_. This generic name was instituted by Lindley and Hutton[1079] for tree-fern stems from the English Coal-Measures showing circular or oval scars arranged quincuncially. The vascular tissue of the petiole is represented by a =U=-shaped impression on the scar, the ends of the =U= being incurved, or by a closed oval ring with a wide-open and inverted =V= near its upper end. The surface between the leaf-scars bears the impression of adventitious roots. _Caulopteris_ is represented, in the Upper Coal-Measures of England, by _C. anglica_[1080] Kidst. The species _C. peltigera_ (fig. 298, A), originally described by Brongniart as _Sigillaria_, illustrates the closed form of leaf-trace and, as Zeiller suggests, it is the cast of a _Psaronius_ stem which possessed a vascular system on the same plan as that of _P. infarctus_. _C. Saportae_[1081] illustrates the open =U=-shaped type of petiole stele. _Caulopteris peltigera_ has scars measuring 6–9 by 4–6 cm.; it occurs in the Commentry Coal-field of France in association with the fronds known as _Pecopteris cyathea_, a species which Kidston regards as identical with _P. arborescens_[1082]. ii. _Megaphyton_.