PROCEEDIN^GS OF THE GEOLOGICAL SOCIETY. 99 



The subject of the jjaper was divided into four heads. In the 

 first an epitome of the views of previous writers on Ulodendron was 

 given. The writers noticed were Steinhauer, Ilhode, Allan, Konig, 

 Sternberg, Brongniart, Lindley and Hutton, Buckland, Hooker, 

 Sauveur, Unger, Goppert, Tate, Geinitz, Goldenberg, MiUer, Eich- 

 wald, Macalister, Dawson, Carruthers, Eohl, Schimper, Weiss, 

 Williamson, Feistmantel, Stur, Thomson, Zeiller, Lesquereux, and 

 Renault. In the second part the Author described the specimens 

 belonging to the species named that he had been able to examine. 



The third part contained the general conclusions as to the nature 

 of Ulodendron at which he had arrived. He commenced by defi- 

 ning the four genera Lepidodendron, Lepidopliloios^ Sigillaria, and 

 Bhytidodendron, as distinguished by the characters of their leaf- 

 scars, and showed t]iSitLej)idode)idron, Sigillaria, and Rhytidodendron 

 occasionally exhibit large scars, arranged in two opposite vertical 

 rows. These are the Ulodendroid scars. They marked, in the 

 Author's opinion, the point of attachment of a caducous appendicular 

 organ, which had in a very few cases been found in position. 

 These appendicular organs were probably sessile cones. Details 

 were given, showing the progressive development of the scars, the 

 obliteration of the normal leaf-scars by the appendicular organs, 

 and the branching of Ulodendroid stems. 



The concluding portion of the paper contained the synonjTiiy at 

 length and full descriptions of the three fossil plants, Lepidodendron 

 Veltheimianum, Sigillaria discojpliora, and >S^. Tai/Iori, together with 

 the horizons and localities in svhich they have been found in Britain. 

 Bothrodendron was shown to be a decorticated form of Ulodendroid 

 stem, and Knorria a cast of the core of Lepidodendron. 



Discussion. 



Mr. Caeeuthers, after expressing his sense of the value of the 

 paper, remarked upon the difiiculty of finding characters of real 

 importance for grouping fossil plants ; hence fossil species and genera 

 are based on very different data from those of recent plants. All 

 the essential characters of the Carboniferous Lycopodiacese, for 

 example, may be found in the recent genus Selaginella. When 

 he himself wrote on the subject he merely accepted the cha- 

 racters of Ulodendron, and his only important difference from the 

 Author was as to the organs borne by the Ulodendroid scars. 

 There was a difficulty in the way of accepting them as cones in the 

 fact that the scar is surrounded by a ring or distinct cicatrix where 

 there was a connexion of tissue ; if so, impressions of leaves within 

 the scar could not be left. All the markings on the lower portion 

 of the scar are circular, indicating the places where vascular bundles 

 passed through. In the upper part they are drawn out. Hence 

 he had considered the organs borne by these scars as aerial roots, 

 such as occur in the Selaginellce of the present day, allied to the 

 Lycopods of the Coal-measures. The important point is, whether the 



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