. Fossil plants : for students of botany and geology . Paleobotany. 372 FILICALES [CH. fossil fern-stems with the habit and, in the main, the structural features of recent tree-ferns. Persistent leaf-bases and sinuous adventitious roots cover the surface of the stems: the vascular system is of the dictyostelic type characteristic of Gyathea (fig. 240, p. 313) and Alsophila. It is by the pattern formed by the vascular tissue on the exposed surface of the leaf-bases that Protopteris is most readily recognised: the leaf-trace has a horse- shoe form with the ends curled inwards and the sides more
. Fossil plants : for students of botany and geology . Paleobotany. 372 FILICALES [CH. fossil fern-stems with the habit and, in the main, the structural features of recent tree-ferns. Persistent leaf-bases and sinuous adventitious roots cover the surface of the stems: the vascular system is of the dictyostelic type characteristic of Gyathea (fig. 240, p. 313) and Alsophila. It is by the pattern formed by the vascular tissue on the exposed surface of the leaf-bases that Protopteris is most readily recognised: the leaf-trace has a horse- shoe form with the ends curled inwards and the sides more or less indented (fig. 277). The generic name Caulopteris is used by some authors in preference to Presl's genus; but Protopteris is more conveniently restricted to Mesozoic Cyathe- aceous stems and Caulopteris to Palaeozoic stems, with the internal structure of Psaronius (see Chap, xxiir.). Stenzel. Fig. 275. A. Coniopteris arguta. (Fertile pinnae ; nat. size.) B. C. Jnjmenophylloides. A, from the Inferior Oolite of Yorkshire (British Museum); B, from Jurassic rocks in Turkestan. applies Caulopteris to Mesozoic stems in which the leaf-trace consists of several separate strands and not of a continuous band. Lower Cretaceous casts of tree-fern stems in the Prague Museum have been described under the names Alsophilina and Oncopteris; the figures of the latter (fig. 276) given by Feist- mantel' and by Velenovsky- show the petiole-bases arranged in vertical rows and characterised by leaf-traces consisting of two separate strands in the form of two Vs lying on their sides. Tree-fern stems described under various generic names are not infrequently found in European Lower Cretaceous rocks: their comparative abundance affords an example of striking changes in geographical distribution since the latter part of the Mesozoic epoch. The Cyatheaceae no longer exist in Europe and the 1 Feistmantel (72). = Velenovsky (88).. Please note that these images are extracted from scanned page images
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