302 PROCElODINjnS OF SOCIETIES. 



Geological Society of Londox. — May Wlh. — Joseph Prestwich, Esq., 

 F.E.S., President, in the chair. The following communication was read : — 

 " On the Structure and Affinities of SigiUaria, Calamites, and Calamoden- 

 dron." By J. W. Dawson, LL.D., F.R.S., F.G.S., Prhicipal and Vice-Chan- 

 cellor of M'Gill University, Montreal. With reference to Sigillaria, a re- 

 markably perfect specimen of the axis of a plant of this genus, from the coal- 

 field of Nova Scotia, was described as having a transversely laminated pith of 

 the Sternhergia type, a cylinder of woody tissue, scalariform internally and 

 reticulated or discigeroiis externally, the tissues much resembling those of 

 Cycads. Medullary rays v^ere apparent in this cylinder ; and it was traversed 

 by obliquely radiating bundles of scalariform vessels or fibres proceeding to 

 the leaves. Other specimens were adduced to show that the species having 

 this kind of axis had a thick outer bark of elongated or prosenchymatous cells. 

 The author stated that Professor Williamson had enabled him to examine 

 stems found in the Lancashire coal-field, of the type of Biuney's Sigillaria 

 vascularis, which differed in some important points of structure from liis spe- 

 cimens ; and that another specimen externally marked like Sigillaria, had 

 been shown by Mr. Carrutliers to be more akin to Lepidodendroti in structure. 

 These specimens, as well as the Sigillaria elegans illustrated by Brongniart, 

 probably represented otlier types of Sigillarioid trees ; and it is not improbable 

 that the genus Sigillaria, as usually understood, really includes several distinct 

 generic forms ; but the type described appeared to predominate in Nova Scotia. 

 The erect Calamites of Nova Scotia illustrate in a remarkable manner the ex- 

 terior sui'face of the stems of these plants, their foliage, their rhizomata, their 

 roots, and their habit of growth. Tlieir affinities were evidently with Equise- 

 tacea;, as Brongniart and others had maintained, and as Carruthers and Schim- 

 per had recently illustrated. The stems were more advanced in structure than 

 those of modern JEquiseta. It was further shown that the leaves of the ordi- 

 nary Calamites are linear, angular, and transversely wrinkled, and different 

 from those of the Asterophyllites properly so called, though some species, as^. 

 comosus, Lindley, are leaves of Calamites. The Calamodendra, as described by 

 Cotta, Binney, and others, ai'e similar in general plan of structure to the Cala- 

 mites, but much more woody plants. Specimens in the collection of Professor 

 Williamson show forms intermediate between Calamites and Calamodendron, 

 so that possibly both may be included in one family ; but much further infor- 

 mation on this subject is required. The tissues of the higher Calamodendra 

 are similar to those of Gymnospermous plants. The wood or vascular matter 

 of the thin-walled Calamites consists of multiporous cells or vessels in such 

 species as have been examined. In conclusion, a table"" was exhibited sliowing 

 the affinities of SigillaricB on the one hand, through Clathraria and Sgringo- 

 dendron with LycopodiacecB ; and on the other hand througli Calamodendron, 

 with Equisetncece ; while in the other direction they presented links of connec- 

 tion with Cycads and Conifers. — Mr. Carruthers said that he was inclined to 

 take a somewhat different view on some of the points mentioned. Some time 

 ago he had, in a paper read to the Society, deduced from the internal structure of 

 Stigmaria, the root of Sigillaria, that the latter was a true cryptogamous plant. 



