IN THE STRATA OF THE CARBONIFEROUS SERIES. 25 



I have been able to obtain, is not much more than four feet, and the lowest 

 part of it is about six feet in circumference. 



In Plate III. is represented a transverse section, viewed by reflected light, 

 and diminished one-half, of a portion of one of these fossil vegetables, found 

 in the lowest exposed bed of shale at Lennel Braes, on the Tweed. 



These stems, as already mentioned, are generally distorted and flattened. 

 They are invested with a coat of carbonized matter, in all respects resem- 

 bling the purer kinds of common coal. No two stems or portions of stems, 

 possess the woody appearances in their interior alike, some retaining them 

 in the centre, others having them distributed in various parts. The ex- 

 terior is irregularly grooved in the longitudinal direction. No indication 

 of branches was observed. The nature of the interior will be best under- 

 stood by referring to the figure. 



Within an external layer of carbonaceous matter/^/Jj^ is exhibited an ir- 

 regularly oval surface, presenting various modifications of colour and texture. 



b, Is the centre, converted into calcareous spar, of which substance all 

 the white rays and veins consist. 



a, a, a, Portions retaining organic texture, and arranged in a radiating 

 manner, from the centre b, towards the circumference, but losing them- 

 selves in the apparently cellular mass of which the greater portion of the 

 stem is composed. 



c, c, c, Portions of the same nature as a, «, «, dispersed irregularly, and 

 presenting in the transverse section an oval or oblong figure, but running 

 continuously through the mass, in its longitudinal direction. 



d, d, d, The mass in which the organic portions are imbedded. It con- 

 sists of crystallizations of calcareous spar, surrounded by carbonaceous and 

 clayey matter, and presents somewhat of a cellular appearance, but is not 

 organic. 



e, e, Indurated argillaceous matter. 



This much is shewn of the external forms and internal arrangement of 

 these remarkable stems, as seen by the naked eye. What the microscope 

 discloses, I now proceed to describe. 



D 



