104 ECONOMIC WOODS OF THE UNITED STATES 



b 6 Pores very small, indistinct to unaided eye. 

 Woods fine-textured and straight-grained; 

 lighter-colored than preceding. Sp. gr. .46- 

 .64. Paper, White* or Canoe Birch, B. 

 papyri/era Marsh. (N, Rn, Pn) 56 ; Gray 

 Birch, B. populifolia Marsh. (N). 



b 4 Woods mostly cross-grained, tough to split. 

 Growth rings usually indistinct. Wood paren- 

 chyma scattered, not in tangential lines or terminal. 



a 5 Wood very dense; sp. gr. about .75. Color 

 reddish-brown or roseate; sap wood yellowish, f 

 Pores minute, well distributed, very numer- 

 ous. Vessels without spirals; bordered pits round; 

 perforations simple; pits into ray cells half-bordered. 

 Rays 3-4 cells wide; homogeneous. Wood fibres with 

 numerous large bordered pits. Apple, PyTUS molus 

 L. (Int.) 57 



b 5 Woods variable in density. The denser ones 

 colorless or light brown. Grain more inter- 

 locked than preceding. Rays 1-5 cells wide; 

 heterogeneous. Vessels mostly without spirals; sca- 

 lariform bordered pits common; perforations sca- 

 lariform with many bars. Pits in wood fibres not 

 conspicuous. 



a 6 Color reddish-brown, often with irregular 

 dark streaks producing " watered " effect on 

 smooth longitudinal surface; sapwood often 

 variegated. Lustre rather dull. Pores 

 minute, abundant, uniformly distributed; 

 tyloses present. Gum ducts occasionally 

 present in peripheral row. Wood mod- 

 erately hard to rather soft; inclined to 

 warp; sp. gr. .50-.60. Vessels without spirals 

 except indistinctly on overlapping ends of seg- 



* The names "red birch" and "white birch" are often used commercially 

 to designate the heartwood and sapwood, respectively, of Betula lenta or B. 

 lutea. 



t In the use of applewood for handles it is customary to steam the sapwood. 

 This treatment produces a rich uniform color resembling that of black cherry. 



