88 ECONOMIC WOODS OF THE UNITED STATES 



b 2 Pores in late wood rarely individually distinct under 

 lens and not few enough to be readily counted; ar- 

 ranged in fan-shaped patches often joined tangen- 

 tially in outer portion. Pores in early wood in few 

 (1-3) rows, usually not crowded; transition to small 

 pores of summer wood abrupt;* usually closed with 

 tyloses except in outer sapwood.f Ray lines on 

 tangential surface often quite long (up to 5 inches) 

 narrow, and straight. Color of wood pale to medium 

 dark brown; not reddish. J Pores in late wood are thin- 

 walled and angular in outline. White Oak Group. § 

 White Oak, Quercus alba L. (C, N) (Frontispiece) 31 ; 

 Bur Oak, Q. macrocarpa Michx. (C, N) (Figs. 13, 14, 

 p. 42); Overcup Oak, Q. lyrata Walt. (C, S); Post 

 Oak, Q. minor Sarg., or Q. stellata Wang. (C, A, S); 

 Oregon Oak, Q. garryana Dougl. (P); Chestnut or 

 Rock Oak, Q. prinus L (N, C) 32 ; Chinquapin or 

 Yellow Chestnut Oak, Q. acuminata (Michx.) Houba, 

 or Q. muhlenbergii Eng. (C, S) ; Swamp White Oak, 

 Q. platanoides (Lam.) Sudw., or Q. bicolor Willd. 

 (N, C); Cow Oak, Q. michuaxii Nutt. (S, C). 

 b Late wood without distinct radial lines or patches, but 

 with tangential or with dotted markings. 

 a x Pores in late wood numerous. (For b x , see p. 92.) 

 a 1 Pores in late wood very small, very numerous and 

 arranged in conspicuous tangential or concentric bands 

 or festoons, broken near early wood; usually producing 

 wavy or zig-zag markings on tangential surface. Wood 

 parenchyma not visible with lens. 



a 2 Pores in early wood in few to several rows except 

 sometimes in narrow growth rings; open. 



* In the white oaks of the South where the growth is rapid the transition 

 from large to small pores is often nearly as gradual as in the red oaks. The 

 pores in the summer wood are also larger and more distinct, but the fact that 

 they are too numerous to count readily with a lens and have thin walls and 

 angular outlines permits ready separation into the white oak olass. A some- 

 what similar structure has been observed in Quercus garryana. 



t In Q. prinus the pores are often open as in the black oak group. 



t One finds occasional exceptions to this statement. Certain grades of 

 white oak are locally known as "pink oak" on account of the color. 



§ For evergreen and live oaks which are diffuse-porous, see p. 98. 



