CALAMODENDRON. 9 



Thuringia/ described the structure of Calamites transitionis (Goeppert) as consisting 

 of a main woody axis of cellular parenchyma, and a lesser inner axis or hollow cylinder 

 with transverse partitions and corresponding constrictions. The first has a smooth out- 

 side, and is formed of cono-cylindrical layers, with indistinct radial divisions, termi- 

 nating inwards in longitudinal ridges, which give to the smaller axis a longitudinally 

 furrowed exterior. The woody structure and a cone-like fruit of Calamites transitionis 

 are figured by Richter. 



§ 10. Dr. Dawson has lately published an elaborate paper ' On the Conditions of the 

 Deposition of Coal, more especially as illustrated by the Coal-measures of Nova Scotia 

 and New Brunswick,'^ wherein he gives his views on Calamodendron and Calamites in 

 the following words (p. 134): — "Calamodendron. — The plants of this genus are quite 

 distinct from Calamites proper. A Calamodendron, as usually seen, is a striated cast, 

 with frequent cross-lines or joints ; but when the whole stem is preserved it is seen that 

 this cast represents merely an internal pith-cylinder, surrounded by a woody cylinder 

 composed in part of scalariform or reticulated vessels, and in part of wood-cells with one 

 row of large pores on each side. External to the wood was a cellular bark ; and the 

 outer surface appears to have been simply ribbed in the manner of Sic/illaria. 



" It so happens that the internal cast of the pith of Calamodendron, which is really of 

 the nature of a Sternbergia, so closely resembles the external appearance of the true 

 Calamites as to be constantly mistaken for them. Most of these pith-cylinders of Cala- 

 modendron have been grouped in the species Calamites approximatus ; but that species, 

 as understood by some authors, appears also to include true Calamites (see Geinitz's 

 ' Steinkohlenformation in Sachsen'), which however, when well preser\'ed, can always be 

 distinguished by the scars of the leaves or branchlets which were attached to the nodes. 



" Calamodendron would seem, from its structure, to have been closely allied to 

 Si(jillaria, though, according to Unger, the tissues were differently arranged, and the 

 woody cylinder must have been much thicker in proportion. 



" The tissues of Calamodendron are by no means infrequent in the coal, and the casts 

 of the pith are common in the sandstones ; but its foliage and fruit are unknown. (Fig. 

 31, Plate VII, a to c.) 



" Calamites. — Nine species of true Calamites have been recognised in Nova Scotia, 

 of which seven occur at the Joggins ; the most abundant being C. Suckovii and C. Cistii. 

 The Calamites grew in dense brakes on sandy and muddy flats. They were unques- 

 tionably allied to Equisetacece, and produced at their nodes either verticillate simple linear 



^ 'Zeitschrift der deutschen geologischen Gesellschaft,' Jalirgang 1864, p. 155. I am indebted to 

 Professor Rupert Jones for calling my attention to this Memoir as these pages were passing through the 

 press. 



2 Read December 20th, 1865. 'Quarterly Journal of the Geological Society,' vol. xxii, pp. 95 — 169, 

 1866. 



2 



