926 MR A. C. SEWARD AND MR A. W. HILL ON THE 



practically identical, and there are at least some Sigillarian stems * in which we cannot 

 discover any structural features distinct from those of the Lepidodendrese. Reasons 

 have already been given for regarding the Dalmeny stem as a Lepidophloios, but 

 whether the younger stems and branches of the French stem should be recognised as 

 belonging to Lepidodendron, Lepidophloios, or Sigillaria must remain an open question. 

 This uncertainty as to the respective anatomical characteristics of these three genera is 

 perhaps a reason in favour of retaining such a generic term as Syringodendron. 



Conclusion. 



The more important anatomical features of the Dalmeny species may be briefly 

 summarised as follows : — 



i. The diploxyloid and mesarch leaf-trace bundles. 



ii. The numerous canals or secretory strands of parenchyma in the phelloderm.f 

 iii. The presence of a fairly regular ring of rather larger secretory strands immediately 



internal to the secondary cortical tissue (phelloderm). 

 iv. The presence of short tracheids on the inner edge of the primary xylem, and the 



numerous and more delicate short tracheal elements external to the corona, 

 v. The delicate and lax nature of the broad inner cortex. 



vi. The parenchymatous pith, which consists in part of elongated cell-filaments, 

 especially in the larger stems ; in smaller branches the pith is solid and 

 composed of more regular cells. 



The character of the parichnos, the nature of the secondary xylem, the presence of a 

 band of secretory tissue in the innermost cortex and other features are not peculiar to 

 this type of the Lepidodendrese. The characters enumerated in the above list must not 

 be regarded as being of specific rank, some at least are certainly shared by allied forms. 

 We are much in need of an exhaustive comparative account of the Lepidodendroid 

 species from which to select features common to the various types and others which 

 may serve as specific characters. The apparent absence of typical phloem has been 

 briefly referred to in the above description ; this is probably a character shared by other 

 species of Lepidophloios and Lepidodendron ; it would seem that we have as yet no 

 satisfactory evidence in these genera of the existence of tissue possessing the ordinary 

 anatomical characters of phloem, and probably the functions associated with the phloem of 



* E.g., a specimen described by Carruthers at the Edinburgh British Association Meeting in 1892 ; but the 

 account was not published in the Annual Report. [Since the above was written a Sigillarian stem has been described 

 by Prof. Bertrand which throws fresh light on the anatomy of this genus. Vide Annals of Botany, 1899.] 



+ We have observed similar secretory strands in the phelloderm of L. vasculare as well as in other species already 

 referred to. [Of. also a figure by Hovelacque (92), in which strands appear to be indicated.] 



