STRUCTURE OF FOSSIL PLANTS 



57 



Vascular Tissue 



Wood. — Protoxylem, tracheids and vessels, 

 long, narrow elements, with spiral or 

 ring -like thickenings, s^ and s\ 

 fig. 31. Compare fig. 81, a, px, for 

 fossil. 



Metaxykm, long elements, tracheids 

 and vessels. Some with narrow pits, 

 as t in fig. 31; others with various 

 kinds of pits. In transverse section 

 seen in fig. 33, w, fossil in fig. 78, w. 



Wood parenchyma. — Soft cells associated 

 with the wood, p in fig. 31. Fossil 

 in fig. 81, B, /. 



Wood sc/erenc/iyma.— Hard thickened cells 

 in the wood. 



Bast — Steve tubes, long cells which carry 

 foodstuffs, cross walls pitted like 

 sieves, s, fig. 32. In transverse section 



in fig. 33- 



Companion cells, narrow cells with 



rich proteid contents, c, fig. 32. In 



transverse section at c, fig. 33. 

 Bast parenchyma. — Soft unspecialized cells 



mixed with the sieve tubes, /, fig. 32. 

 Bast fibres, — Thick -walled sclerenchyma- 



tous cells mixed with, or outside, the 



soft bast. 



/. /' 



Fig. 32 



Cambium. — Narrow cells, like those of the 

 cork cambium, which lie between the 

 wood and bast, and give rise to new 

 tissues of each kind, cb, fig. 33. Com- 

 pare fig. 114, fossil. 



Fig- 33 



