102 ECONOMIC WOODS OF THE UNITED STATES 



plugged at intervals with dark red gum. 

 Gum ducts common. Wood variable in 

 density; sp. gr. .48-71, average .58. Rays 

 mostly 3-5 cells wide, occasionally uniseriate, and 

 few to 100 cells high; somewhat heterogeneous. 

 Wood fibres with bordered pits. Black Cherry, 

 Primus serotina Ehrh. (C, N, S). 



b 6 Color variable from very light to decidedly 

 reddish. Rays on radial surface appear 

 considerably darker than background; 

 variable in size. Pores not crowded, fairly 

 evenly distributed; solitary or in radial 

 groups of 2-3; fairly uniform in size 

 throughout growth ring. Grain often 

 curly, " landscape," or "birds-eye." Rays 

 homogeneous. Wood fibres with bordered to simple 

 pits. Maple.* 53 



a 7 Part of the rays comparatively large, 

 broader than the pores, conspicuous. 

 Pith flecks rare. Growth rings very dis- 

 tinct on account of deeper-colored late 

 wood. Wood dense ; ave. sp. gr. .69. Rays 

 5-7 cells wide with intermediate rays uniseriate. 

 Hard, Sugar, or Rock Maple, Acer sac- 

 charum Marsh. (N, C.) 54 ; Black Maple, 

 A. nigrum Michx. (N, C). 



b 7 With less variation in the size of the rays, 

 the large ones not so broad as the pores; 

 low, inconspicuous. Growth rings often 

 indistinct. Woods variable from soft to 

 moderately hard. Uniseriate rays few. 



a 8 Color deep and rich. Pith flecks un- 

 common. Sp. gr. .49. Oregon Maple, 

 A, macrophyllum. (P). 



* Boxelder or ash-leaved maple, Acer negundo L., or Negundo aceroides 

 Moench. (N, C, S, R), and its varietal form, californicum (T. & G.) Sarg. (Ps), 

 produce rather light (sp. gr. .43), soft woods, cream-colored or yellowish white. 

 The pores are small and numerous; often in radial groups of 2-6. Rays are 

 without color. 



