Manchester Memoirs, Vol. Ivii. (19 13), No. 18- 11 



The structure of the secondary wood, consisting as it 

 does largely of tracheids, with one or two rows of pits, 

 points to Araucarian affinity of our fossil, though the 

 considerable number of scalariform tracheids which pre- 

 cede the pitted elements seems to indicate a primitive 

 form of that group. As Thompson" has now confirmed 

 the old view of the derivation of the Araucarineae from 

 the Cordaitalean stock, we may expect our fossil to 

 show some features of the latter. The secretory canals 

 referred to above may be considered in that light as well 

 as the large number of scalariform elements. Moreover, 

 we must remember that even among the Cordaitales we 

 now know of members with bordered pits in one or two 

 rows ; for this is one of the diagnostic characters of Meso- 

 xylon poroxylcides described by Scott.'- 



The remains of groups of tracheids possibly repre- 

 senting primary centripetal xylem may also be regarded 

 as of a primitive nature, and, ill-defined as these are, they 

 may indicate, as Zalessky" has said of the same pheno- 

 menon in Dadoxylon (Mesopitys) Tcliiliatclieffi, " la marche 

 probable des modifications de la structure mesarche du bois 

 primaire des anciens types gymnospermes dans la direction 

 de celles qui est propre aux especes actuellement vivantes 

 du meme groupe." 



We obtain no help towards the identification or classi- 

 fication of our fossil plant from the fact that it possesses 

 foliar gaps and double leaf-traces. These characters it 

 shares both with the Araucarineae^^ and the Cordaitales. 



1 ^ Loc. cit. , p. 42. 



^- Scott, D. II. "The Structure of J/esoxj'/on Lo»i ax it and A/, poro- 

 xyloides." Annals o; Botany, vol. xxvi., Oct. 1912. 



^* Zalessky, |M. D. "Etude sur Tanatomie du Z'afl'<?.r_j'/c?« Tchihatcheffi, 

 Goeppert. Memoires uu Co/iii/c' geologiqtie St. Petosbourg, 1911, p. 21. 



^■' Thompson, loc. cit. 



