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.
Fig. 298.
- Caulopteris peltigera.
- 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].