108 ECONOMIC WOODS OF THE UNITED STATES 



a 4 Color of wood reddish-brown, usually variable. 

 Lustre dull. Texture coarse. Pores very 

 abundant, readily visible to unaided eye; smaller 

 in late wood and sometimes in irregular tan- 

 gential arrangement in wide growth rings. 

 Wood light and soft but fairly tough; sp. gr. .41- 

 .47. Wood parenchyma terminal in 1-2 rows, usually 

 invisible with lens. Vessels without spirals; perforations 

 simple; pits into ray cells simple. Rays uniseriate; het- 

 erogeneous. Black Willow, " Brown Cotton- 

 wood," Salix nigra Marsh. (C, N, S, Rs, Ps). 64 



b 4 Color pale brown, grayish or white. Woods 

 very light and soft. Growth ring terminated by 

 fine light-colored line of parenchyma, more or 

 less distinct. Vessels without spirals; perforations 

 simple; pits into ray cells simple. Rays uniseriate; 

 homogeneous. 



a 5 Texture rather coarse and wooly. Lustre 

 dull. Pores abundant, visible without lens, 

 smaller in late wood and sometimes in irregu- 

 lar tangential arrangement in wide growth 

 rings. Sp. gr. .32-.4S, average about .40. 

 Poplar, Cottonwood, Populus deltoides Marsh. 

 (N, C, S, R) 65 ; P. heterophylla L. (S, C); P. 

 trichocarpa T. J. G. (P). 



b 5 Texture very fine and silky. Lustre high. 

 Pores abundant, usually invisible without 

 lens; fairly uniform in size and arrangement. 

 Sp. gr. .36-51, mostly .40-.45. Aspen, Pop- 

 lar, Popple, P. tremuloides Michx. (N, C, R, 

 P); P. grandidentata Michx. (N, C). 66 



