MACROSCOPIC STRUCTURE. 



but small and bordered by pale parenchyma, and therefore 



visible as bright points 



in the surrounding darker 



tissue. 



chyma 



Tangential paren- 







is not visible (Fig. 



This is the main 

 difference between ashwood 

 and hickory- wood, the latter 

 possessing visible white tan- 

 gential parenchyma that 

 is parallel to the annual 

 rings (Fig. 12A). The rays 

 are scarcely visible. Sum- 

 mer-wood somewhat darker 

 than spring-wood. Owing 

 to the large pores, the 

 borders of the annual rings 

 are distinct. 



Radial Section. - Tli<> 

 borders of the annual rings 

 are marked byeurved gr<> 

 of the large vessels in the 

 spring- wood. The medul- 

 lary rays ;ire slightly visible 

 as very numerous, narrow, 

 bright bands or patches. 



Tangential Section. Ves- 

 sels as in the radial section, 

 but in shorter lengths. The 

 finer pores of the summer- 

 wood with their parenchyma 

 are seen only on very smooth 

 sections, according to the 

 angle of incidence of light, 

 as brighter or darker line 

 lines. The sapwood is very 

 broad ; the heartwood (light 

 brown) at first resembles the sapwood, but becomes darker 

 as the wood dries. 



1 1. Type of Ashwood (Fraxinus). 







Fig. 12. 

 A IhVkovy-wocxl. P. 



(Slightly enlarged.) 



