W. Carruthers — The Forests of the Coal Period. 293 



fruit — have been formed into numerous genera, whicli have been 

 referred to widely different positions in the vegetable kingdom. 



Considerable diversity of structure is to be found in those stems 

 which are referred to Calamites. I shall ask your attention to one of 

 these forms which I have described/ and which is beautifully illus- 

 trated by a series of drawings, recently published, of specimens in Mr. 

 Binney's collection.'^ This stem was composed of a central medulla 

 surrounded by a woody cylinder, composed entirely of scalariform 

 vessels and a thin cortical layer. The medulla penetrated the woody 

 cylinder by a series of regular wedges, which were continued, as 

 delicate laminge of one or two cells in thickness, to the cortical layer. 

 The cells of these laminae were not muriform ; their longest diameter 

 was in the direction of the axis. The wedges were continuous and 

 parallel between each node. As the axial appendages were produced 

 in whorls, the only interference with the regularity of the tissues 

 was by the passing out through the stem at the nodes of the vascular 

 bundles which supplied these appendages. As the leaves of each 

 whorl were (with one or two exceptions) opposite to the interspaces 

 of the whorls above and below, there was also at each node a re- 

 arrangement of the wedges of vascular and cellular tissues. 



The stem is described as having been fluted on the outer surface. 

 This error had its rise in the specimens examined, being only casts 

 in the amorphous substance of the rock of the medullary cavity, sur- 

 rounded by a thin film of coal representing the cylinder of wood. On 

 the death of the plant, the cellular medulla decayed, while the woody 

 cylinder was still able to retain its original form. The hollow interior 

 was filled with some of the mud or sand in which the plant was buried. 

 In the course of time this offered greater resistance to the pressure of 

 the beds above than the originally hard cylinder of scalariform tissue, 

 now softened by the moisture in which it had so long lain : the more 

 indurated amorphous axis on pressure necessarily produced its cha- 

 racteristic ridges and furrows on the smooth outer surface of the film 

 of coal. This coal is described as the cortex or bark, and stems 

 exhibiting only the rocky casts of the medullary cavity are called 

 decorticated specimens ; but, besides the cortical layer, they have 

 also been deprived of all that remained of their woody tissue. 



The stem terminated below somewhat suddenly in a blunt cone, 

 the internodes of which were slightly developed ; and from the nodes 

 were given off whorls of large roots, which again gave off innumerable 

 branching rootlets (Pinnularia). 



The stem or main axis was simple, supporting numerous branches 

 arranged in whorls, which again produced numbers of whorled leaves. 

 Three different forms of leaves have been formed into as many genera. 

 When the structure of the fruits associated with them is better known, 

 by the discovery of better preserved specimens, it is possible they 

 may be found to constitute three genera, but there are no characters 



^ On the Structure and Affinities of Lepidodendron and Calamites. Trans. Bot. 

 Soc. Edin. vol. viii. (1866) p. 495, PI. 8 and 9. 



"^ On the Flora of the Carboniferous Strata, Part I. By E. W. Binney. Palaeont. 

 Soc. vol. xxi., 1868. 



