PROP. W, C. WILLIAMSON OS CALAMODENDRON. 255 



XVI. On the Relations of Calamodendron to Calamites. 

 By Professor W. C. Williamson, LL.D., F.R.S. 



Read October 5th, 1886. 



[Plates XIV., XV., & XVI.] 



The relations in which the genus Calamodendron of 

 Brongniart stands to that of Calamites, originally estab- 

 lished by Suckow, and adopted by Brongniart and later 

 authors, are involved in a considerable amount of confusion; 

 this confusion is partly due to some indefiniteness in the 

 statements of Brongniart himself on the subject, and 

 partly to differences of opinion existing amongst palseo- 

 botanists as to what those relations really are. 



In 1828 Brongniart published his 'Prodrome d^une 

 Histoire des V^getaux Fossiles/ in which, for the first time, 

 a serious attempt was made to classify the various types 

 of fossil vegetation. In that volume Brongniart divided 

 the family of the Equisetacees into the two genera Equi- 

 setum and Calamites, thus recording his opinion that the 

 latter plants were true members of the Equisetaceous 

 family. 



But in 1849 Brongniart published, in the ' Dictionnaire 

 universel d^ Histoire naturelle,' his " Tableau des Genres 

 de Vegetaux Fossiles." In the interval he had become 

 acquainted with some fossils from Autun, belonging to 

 deposits occupying the boundary-line between the upper- 

 most beds of the Carboniferous series and the lowest 

 Permian ones. These fossils had meanwhile been studied 

 by M. Cotta, who gave to them the generic name of 

 Calamitea. 



It appears that, under this generic term, Cotta compre- 

 hended some Conifers ; two plants, however, to which he 



