86 ECONOMIC WOODS OF THE UNITED STATES 



present in variable amount; often conspicuous. Resin ducts 

 absent. Gum ducts sometimes present in a few species. Rays 

 varying from minute to large and conspicuous. 



A Ring-porous Woods. Largest pores localized in a distinct 

 ring or band in early wood.* (For B, see p. 95.) 



a Late wood with radial lines or patches (frequently 

 branched or fan-like) composed of small pores and paren- 

 chyma, usually lighter colored than remainder of wood; 

 also with parenchyma in fine concentric lines, distinct to 

 indistinct.! (For b, see p. 88.) 



a^ Rays all very fine, inconspicuous. J Woods soft to 

 moderately hard; stiff but not strong; sp. gr. .45-.59. 



a- Pores in early wood few, small, nearly circular, open, 

 and rather widely separated in a single row. Color 

 of wood light brown or roseate. Odorless and taste- 

 less. Vessels without spirals; bordered pits circular, teudinf:; 

 to become scalariform in small vessels; perforations simple with 

 tendency to scalariform with few bars; pits into ray cells either 

 half-bordered or simple. Rays uniseriate (occasionally bise- 

 riate in median portion), 5-15 cells high; more or less heteroge- 

 neous. Western Chinquapin, Castanopsis chnjsophylla 

 de C. (P). 



b^ Pores in early wood very numerous, large, mostly 

 oval or elliptical, open, and in a bi'oad zone. Color 

 of wood brown; stains blue-black in contact with 

 iron when moist. Odor of fresh wood mild but dis- 

 tinct. Taste somewhat astringent due to tannin 

 content. (Microscopic features given in preceding apply 

 here.) Chestnut,§ Castanea dentata Borkh. (C, N).^' 



* This feature may be obscure in very narrow growth rings where the pro- 

 portion of late wood is so reduced that the wood apfjcars diffuse-porous. 



t The visibility of wood parenchyma is usually increased by moistening 

 the smoothly cut end of the specimen. 



X The distinctness of the rays refers to the cross section unless otherwise 

 stated. 



§ The chinquapin chestnut {Castanea pumila Mill.) is a small southern tree 

 of only local importance for fence posts and fuel. The wood is mostly harder, 

 heavier and of slower growth than the other species. The structures of the 

 two woods are nearly identical. 



