194 



EVIDENCE OF THE FOSSIL FLORA. 



rather less distinct than the transverse one : in the section 

 parallel to the radius of the stem or bole, the circular discs of 



Fig. 66. 



INTEBNAL STRUCTUllE OF LIGNITE OF LOWER (MIDDLE) OLD RED SANDSTONE. 



a. Transverse section. 



b. Longitudinal section (parallel to radius, or medullary rays J. 



c. Longitudinal section (tangental, or parallel to the hark). 



(Mag. forty diameters.) 



the coniferse were at first not at all detected ; and, as since 

 shown by a very fine microscope, they appear simply as double 

 and triple lines of undefined dots (5), that somewhat resemble 

 the stippled markings of the miniature painter ; nor are the 

 openings of the medullary rays frequent in the tangental sec- 

 tion (^. e. that parallel to the bark) (c) ; but nothing can be 

 better defined than the peculiar arrangement of the woody 

 fibre, and the longitudinal form of the cells. Such is the cha- 

 racter of this, the most ancient of lignites yet found, that 

 yields to the microscope the i)eculiarities of its orifi;inal struc 



