SIGILLARIA 221 



is partially preserved in these specimens. In the outer 

 cortex the bundles assumed a more horizontal direction. 

 In some of the sections they show a diploxylic structure. 

 In this species M. Renault first made the interesting 

 observation that two large lacunae accompanied the 

 bundle on its outward course, one on each side, form- 

 ing, at the point where they entered the leaf, the two 

 lateral prints on the foliar scar, which are now termed 

 the parichnos. In this and in other species of Sigillaria 

 M. Renault subsequently showed that the lacunae, which 

 are surrounded by a definite sheath of radially elongated 

 cells, were filled by a delicate cellular tissue traversed 

 by secretory canals (see Fig. 92, A). The same 

 observer also proved, by anatomical investigation, that 

 the well-known prints on the partially decorticated 

 Syringodendron stems are of the same nature, though 

 here much enlarged. The identity of Syringodendron 

 with Sigillaria thus received fresh demonstration. 1 



In Sigillaria, as in Lepidodendron, the parichnos- 

 strands start from the inner cortical zone. That their 

 function was in part secretory is highly probable, but 

 the persistence and enlargement of the parichnos on 

 the surface of old stems suggests a respiratory function, 

 like that of lenticels. 



The outer cortical layers of 5. spinulosa have a 

 peculiar structure. There is a broad zone of secondary 

 periderm, but its tissue is not uniform ; it is made up 

 of radial anastomosing bands of narrow elongated cells, 

 while the meshes between these bands are occupied by 



1 See also K. H. Coward, ' ' On the Structure of Syringodendron, the 

 Bark of Sigillaria" Mem. and Proc. Manchester Lit. and Phil. Soc. vol. li. 

 Part ii. 1907. 



