SIGILLARIA 



209 



which is dot -like, or transversely elongated, is the 

 smallest, but the most important, for anatomical 

 investigation has shown that this alone represents the 

 vascular bundle of the leaf. The two lateral prints are 

 vertically elongated, and are either straight or crescent- 

 shaped, with the concavity directed inwards. These 

 lateral marks are of the same nature as the parichnos of 

 Lepidodendron. I m - 

 mediately above the 

 scar, and sometimes 

 seated in a depression <r/A 

 edge, is 

 print, 

 evidently represents 

 the ligular pit (Fig. 

 88,/^). We thus see 

 that, except for trifling j 

 details, there is no 

 difference in morpho- 

 logy between the leaf- 

 scars of Sigillaria 

 and those of Lepido- 

 dendron. 



When we come to 

 the arrangement of the scars, we meet with considerable 

 variations within the genus ; these variations have been 

 used for the distinction of subgenera, which some 

 authors have even erected into distinct genera. We 

 shall see, however, that in the light of our present 

 knowledge very little, if any, taxonomic value can be 

 attached to these differences, though they are worth 

 noting for descriptive purposes. 



H 



Fig. 88. — Sigillaria Brardi (Leiodermaria type). 

 Part of surface of stem, showing five leaf-scars. 

 Ig, ligule ; v.b., print of vascular bundle; pa, 

 parichnos. X *\. After Weiss. 



