426 



THE CARBONIFEROUS SYSTEM. 



(Fig. 160). It is cylindrical, but somewhat flattened, being one inch 

 and two-tenths in its least diameter, and one inch and seven-tenths 

 in its greatest. The diaphragms, or transverse partitions, appear to 

 have been continuous, though now somewhat broken. They are rather 

 less than one-tenth of an inch apart, and are more regular than is usual 

 in these fossils. The outer surface of the pith, except where covered 

 by the remains of the wood, is marked by strong wrinkles, correspond- 

 ing to the diaphragms. The little transverse ridges are in part coated 

 with a smooth tissue similar to that of the diaphragms, and of nearly 



the same thickness. 



Fig. 160. — Sternhergia Pith of DculoxyJon. 

 A B C 



A, Specimen ; nat. size, showing remains 



of wood at (a) (a). 



B, Junction of wood and pith ; magnified. 



C, Cells of the wood of do. (aa); (6) Me- 



dullary ray ; (c) Areolation. 



D, Longitudinal section of another speci- 



men with thick coaly envelope repre- 

 senting the w^ood. 



E, Flattened trunk, with Sternhergia pith 



at (a) ; reduced. 



F, Cellular tissue of pith. \ 



When traced around the circumference or toward the centre, the 

 partitions sometimes coalesce and become double, and there is a ten- 

 dency to the alternation of wider and narrower wrinkles on the surface. 

 In these characters and in its general external aspect, the specimen 

 perfectly resembles many of the ordinary naked Sternbergiaj. 



On microscopic examination, the partitions are found to consist of 

 condensed pith, which, fi'om the compression of the cells, must have 

 been of a firm bark-like texture in the recent plant (Fig. 160, F). The 

 wood attached to the surface, which consists of mei"ely a few small 

 splinters, is distinctly coniferous, with two and three rows of discs on 



