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VII. On the Organization of the Fossil Plants of the Coal-measures. — Part VIII.Ferns (continued) and Gymnospermous Stems and Seeds. By W. C. Williamson ,F.R.S., Professor of Natural History in the Owens College, Manchester .
Received May 2,—Read May 18, 1876.
[Plates 5-16.]
In one of his valuable Memoirs on the Fossil Plants of the Carboniferous deposits ofFrance* M. Renault has described the stems of two fossil Ferns, to both of whichexamples characteristic petioles are attached. In these stems the chief vascular orpseudo-vascular elements are not scattered over the transverse section of the stem indetached bundles, as is usual amongst living Ferns , but they are gathered together so asto form an axial cylinder, enclosing an irregular, central, radiating medulla composed ofparenchymatous tissue. In the sixth of this series of memoirs I figured (plate 58.fig. 51) a transverse section of a similar vascular axis, but without either petioles oreven any investing cortical layer attached to it. In one of M. Renault ’s examples thepetioles associated with the stem were identical with those to which Corda gave thename of Zygopteris. In the second species, to which M. Renault assigned Corea ’sgeneric name of Anachoropteris, the transverse section of the petiolar vascular bundleresembles that of Osmunda and Todea , as M. Renault has correctly indicated ( loc. cit.p. 176). He also points out the difference existing between the closed vascular cylindersof the stems of these two Ferns and the corresponding bundles of most living types, butthinks that something similar to them may be found amongst the Ophioglossums.
I am indebted to my indefatigable auxiliary, Mr. J. Butterwortii, for an interestingstem of the same type which he obtained from the rich reservoir of fossil plants nearOldham. The specimen was about lj inch in length, whilst its somewhat oval, trans-verse section had a maximum diameter of about an inch. The external surface wasstrongly marked by an irregular series of transverse ridges and furrows, represented infig. 1, and which may some day contribute to the identification of the fronds with whichthis stem should be associated. There are about twenty-four of these ridges, withcorresponding intermediate furrows, to each vertical inch of the stem. On making atransverse section of the specimen I found a central vascular cylinder closely resemblingthat seen inM. Renault ’s specimen of Zygopteris Brongniarti ( l. c. pi. 3. fig. 1 ,a), alongwith two or three secondary ones, of varying dimensions, dispersed over the area of the* “ Etude de quelques ve'getaux silicifies des environs d’Autun,” par M. Renault , Annales des SciencesXaturelles, 5 e serie, Bot., t. xii. (Cahier no. 3).
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