ULODENDRON AND HALONIA 167 



appearing to confirm by direct evidence an idea which 

 had long previously been suggested. The Ulodendra, 

 then, were supposed to represent the fertile branches 

 of various species of Lepidodendron {e.g. L. Veltheimi- 

 anum), Bothrodendron, and perhaps Sigillaria also, 

 which thus bore their fructifications on thick stems, 

 and not on terminal twigs. The peduncle, represented 

 by the print within the scar, was assumed to be quite 

 short, so that the base of the almost sessile strobilus was 

 in contact with the leafy surface of the main axis ; the 

 large cup-shaped scar appeared to have owed its origin 

 to the mutual pressure between the two organs. The 

 great size of the scars in some cases was still, however, 

 unaccounted for, their shape being inconsistent with 

 dilatation by secondary growth. 



Mr. D. M. S. Watson - 1 has quite recently pointed out 

 the great difficulties involved in the current interpreta- 

 tion of the Ulodendroid scar, and the inadequacy of 

 the evidence in its support. He maintains that the 

 scars are those of caducous branches, which were 

 attached to the whole area of the scar, the umbilicus 

 corresponding to the central cylinder and the dots and 

 radial marks on the scar representing the leaf-traces of 

 the branch. For certain cases, at all events, his inter- 

 pretation appears to correspond best with the observed 

 facts, though various difficulties remain. 



The other form of stem to be considered — that 



Edinburgh Geo/. Soc. vol. iii. 1880. Cf. Solms-Laubach, Fossil Botany, 

 English edition, p. 208. Kidston, "On the Relationship of Ulodendron 

 to Lepidodendron, etc. ," Ann . arid Mag. Nat. Hist. vol. xvi. 1885 ; Zeiller, 

 " Sur les Ulodendron et Bothrodendron," Bull. Soc. Giol. de France, ser. iii. 

 t. xiv. 1885. 



1 "On the Ulodendroid Scar," Mem. and Proc. Manchester Lit. and 

 Phil. Soc. vol. Iii. Part i. 1908. 



