STRUCTURE OF DICOTYLEDONOUS STEM. 



411 



Fig. 215, the Medullary Rays seem'to run parallel to each other, in- 

 stead of radiating from a common centre. They are very narrow : 

 but are so closely set 



together, that only FlG> 215 



two or three rows 

 of Woody Fibres (no 

 ducts being here 

 present) intervene 

 between any pair of 

 them. In the Longi- 

 tudinal Section 

 taken in a Radial 

 direction (Fig. 216), 

 and consequently 

 passing in the same 

 course with the 

 Medullary Rays, 

 these are seen as 

 thin plates (a, a, a) 



made-up of super- Portion of Transverse Section of large Stem of 

 i p n Coniferous Wood (fossil), showing part of two 



posect lyeils very aj^^i Layers, divided at a, a, and traversed 

 much elongated, by very thin but numerous Medullary Rays. 



Fig. 216 



Fig. 21< 



Portion of Vertical Section of the same 

 Wood, taken in a Radial direction, showing 

 the glandular Woodv fibres, without Ducts, 

 crossed by the Medullary Rays, a, a. 



Portion of Vertical Sec- 

 tion of the same Wood, 

 taken in a Tangential direc- 

 tion, so as to cut across 

 the Medullary Rays. 



