220 



LYCOPODIALES 



[CH. 



dendron, and it is noteworthy that traces of partially- 

 disorganised tissue, described as large canals, in the region 

 external to the secondary wood, bear a resemblance' to the 

 secretory tissue of Lepidodendron. 



Other interesting features are presented by the structure of 

 the outer cortex and the parichnos. The outer cortex in the 

 leaf-scar region is composed of parenchyma, but for the most 

 part it consists of radially elongated groups of thin-walled 



Fig. 202. A. Sigillaria elegam Brongn. (Section in Dr Kidston's Collection 

 cut from the specimen shown in fig. 193, D.) 

 B, C. Sigillaria elongata Brongn. It, leaf-trace. (From specimens 

 in the collection of Prof. Bertrand.) 



parenchyma enclosed in a framework of thicker-walled and 

 elongated elements (fig. 200, B, c^). This type of cortex, to 

 which Brongniart applied the name Dictyoxylon , would produce 

 a cast in the case of a partially decorticated stem characterised 

 by a surface formed of irregularly oval and raised areas bounded 

 by narrow grooves ; the greater prominence of the former being 

 due to the more rapid decay of the softer tissue, which would 



1 Eenault and Grand'Eury (75) PI. i. fig. 5. 



