The Carboniferous Arborescent Lepidodendra. 35 



disposition is easily traced. In the majority of the speci- 

 mens of these barks collected from horizontal beds of soft 

 shale, the normally prominent leaf-cushions have been so 

 mechanically compressed that all traces of their prominence 

 have disappeared. The branching of these plants is uni- 

 versally dichotomous. Such is an outline of the funda- 

 mental characteristics of these Carboniferous Lycopods ; 

 thus far intelligent palseobotanists, like my old friend Graf, 

 zu Solms and others, are substantially in agreement with 

 me. But we now have to deal with facts respecting the 

 explanations of which we were not in agreement. These 

 differences related to problems connected with the growth 

 of these plants, and especially affecting the organisation 

 and development of the tissues constituting the Primary 

 Xylem or central part of the stele. In his " Fossil 

 Botany," Professor Solms stated, on p. 230 of the English 

 Edition, the points on which he differed from my con- 

 clusions on the debated question, and there are other 

 friends who agreed with his opinions. When preparing 

 for publication Part III. of my series of memoirs 

 " On the Organisation of the Fossil Plants of the Coal 

 Measures," I arrived at the conclusion that the young 

 twig was merely an infantile representative of the matured 

 stem ; that young and small twigs only differed from 

 matured stems and branches so far as the age and growth 

 of the latter altered their development and organisation ; 

 and in Plate I., Figs. 2, 3, 4, and 5, I represented transverse 

 sections of the Primary Xylem of the stele, as it appeared in 

 branches of various dimensions, and which I regarded as 

 representing what we should have found if we 'could have 

 made such a series of sections of the same living branch at 

 various parts of its length. But my friendly opponents 

 denied the possibility that Figs. 8 and 11 of the series 

 referred to above, ever were, or could have been, in the 

 condition represented by Figs. 3 and 4, but that each of 



