STRUCTURE OF FOSSIL PLANTS 



57 



VASCULAR TISSUE 



Wood. Protoxylem, tracheids and vessels, 

 long, narrow elements, with spiral or 

 ring - like thickenings, j 1 and s 2 , 

 fig. 31. Compare fig. 8i,A, p x, for 

 fossil. 



Metaxylem, 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,/ in fig. 31. Fossil 

 in fig. 8 1, B,/. 



Wood sclerenchyma. Hard thickened ceils 

 in the wood. 



Bast. Sieve 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, p, 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 



