344 CALAMITES. [CH. 



shaded portion of the specimen is covered by a layer of coal 

 representing the carbonised wood and cortex, which has been 

 moulded on to the sandstone pith-cast. In fig. 77 (p. 316) a 

 fairly thick root is seen, in organic connection with one of the 

 nodes, JSf 3, and on iV 2 there is a scar of another root. 



There are certain external characters by which one itlaj 

 often recognise a Calamitean root. There is no division into 

 nodes and internodes as in stems, and as the pith of the root 

 was usually solid the parallel ribs and grooves of stem-casts are 

 not present. In smaller flattened roots there may sometimes 

 be seen a central or excentric black line representing the stele, 

 and the surface of the root presents a curious wrinkled or 

 shagreen texture, probably due to the shrinkage of the loose 

 lacunar cortex. The occasional excentric position of the stele 

 is no doubt due to the displacement of the vascular cylinder 

 as a result of the rapid decay of the cortical tissues. In the 

 Bergakademie of Berlin there are some unusually good examples 

 of Calamite casts bearing well-preserved root-impressions ; these 

 include the original specimens figured by Weiss \ 



No doubt some of the roots figured by various writers under 

 the names Pinmdaria^ and Hydatica^ belong to Calamites, 

 but it is often impossible to identify detached specimens with 

 any certainty. 



The section figured diagrammatically in fig. 91 A shows 

 the characteristic single series of large lacunae, I, in the middle 

 cortical region. In the centre there is a wide solid pith sur- 

 rounded by a ring of vascular tissue, x. The appearance of the 

 middle cortex is very like that of the stem of a water-plant 

 such as Myriophyllum, the Water Milfoil ; it shows that the 

 Calamite roots grew either in water or swampy ground. In 

 fig. 91 5, the root characters are clearly seen; the centre of 

 the stele is occupied by large parenchymatous cells which are 

 rather longer than broad in longitudinal view; at the peri- 

 phery there are four protoxylem groups px, alternating with 

 four groups of phloem, ph, the latter being situated a little 



' Weiss (76), (84). 



- For references, vide Kidston (86), p. 58. 



s Artis (25), PI. v. 



