xv] 



LEPIDODENDRON 



179 



distance below the apex of each area there is a more or less 

 circular prominence or depression (fig. 187, B) and on a few of 

 the areas there are indications of a groove (lig. A, g) extending 

 from the raised scar to the pointed base, as at g, g. 



In examining the graphitic layer on the surface of the 

 South African specimen shown in fig. 187, A, use was made of 

 a method recently described by Professor Nathorst'. A few 



Fig. 187. Lepidodendron australe. Fig. A, nat. size. 



drops of collodion were placed on the surface, and after a short 

 interval the film was removed and mounted on a slide. The 

 addition of a stain facilitated the microscopic examination and 

 the drawing of the collodion film. The cell-outlines (fig. 187, C) 

 on the surface of the polygonal areas may be those of the 

 epidermis, but they were more probably formed by a sub- 

 epidermal tissue ; the scar, which interrupts the continuity of 

 the flat surface, may mark the position of a leaf-base, or, 



1 Nathorst (07) ; Bather (07) ; (08). 



