472 



CALAMITES. 



[Ch. XXIV 



for, like the common "horsetail," they usually exhibit little more 

 than hollow jointed stems, furrowed externally. (See figs. 522, 523, 

 524.) 



Mr. Salter stated to me many years ago his conviction that the 

 calamite as frequently represented by palaeontologists was in an in- 

 verted position, and that the conical part given as the top of the stem 

 was in truth the root. This point Dr. Dawson and I had opportuni- 

 ties of testing in Nova Scotia, in 1853, where we saw many erect 

 calamites, having their radical termination as in the foregoing figure 

 (fig. 524). The scars, from which whorls of vessels have proceeded, 

 are observed at the upper, not the lower, end of each joint or inter- 

 node.* The specimen (fig. 522), therefore, is no doubt the lower end 

 of the plant, and I have therefore reversed its position as given in the 

 Avork of Lindley and Hutton. 



M. Adolphe Brongniart, following up the discoveries of Germar 

 and Corda, has shown in his "Genres de Vegetaux Fossiles," 1849, 

 that many Calamites cannot belong to the Uquiseta, nor probably to 

 any tribe of flowerless plants. He conceives that they are more 

 nearly allied to the Gymnospermous Dicotyledons. They possessed 

 a central pith, surrounded by a ligneous cylinder, which was divided 

 by regular medullary rays. This cylinder was surrounded in turn by 

 a thick bark. Of fossil stems having this structure Brongniart 

 formed his genus Calamodendron, which includes many species re- 

 ferred by Cotta, Petzholdt, and 

 TJnger to the genus Calamitea. 

 The Calamodendron is described 

 as smooth externally, its pith 

 being articulated and marked 

 with deep external vertical 

 striae, agreeing, in short, with 

 what geologists commonly call 

 a Calamite. Since the appear- 

 ance of Brongniart's essay, Mr. 

 E. "W. Binney has made many 

 important discoveries on the 

 same subject ; and Mr. J. S. 

 Dawes has published a more 

 complete account of this singu- 

 lar fossil.f Their views have 

 been confirmed by Professor 

 Williamson of Manchester, who 



Fig. 525. 



Portion of a Calamite, near the base, showing the 

 external cylinder, connected by radiating ves- 

 sels with the cast of the pith. 



Communicated by Prof. C. Williamson. 



has communicated to me a 

 specimen figured in the annexed 

 cut (fig. 525), in which we see 



* See Dawson, Geol. Quart. Journ., 1854, vol. x. p. 35. 

 f Quart. Journ. Geol. Soc. Lond., 1851, voL vii. p. 19G. 



