ECONOMIC WOODS OF THE UNITED STATES 107 



b 2 Rays indistinct to unaided eye and often with lens, 

 except for occasional aggregate rays in Alnus oregona. 



a 3 Rays fairly distinct with lens. 



a 4 Wood of very fine texture. Pores minute, in- 

 visible without lens, very uniformly distributed. 

 Color pale yellow to nearly white. Lustrous. 

 Growth rings terminated by fine line of wood 

 parenchyma. Pith flecks absent. Wood light, 

 soft, compact, tough, often with curly or inter- 

 locked grain; sp. gr. .42-.50. Vessels with spirals; 

 perforations simple; pits into ray cells half-bordered; 

 often grouped. (Fig. 3, C, p. 24). Rays all uniseriate; 

 heterogeneous. 



a 5 "Ripple marks" distinct on tangential sur- 

 face; fairly regular; 65-70 per inch; all ele- 

 ments storied. Yellow Buckeye, JEsculus 

 octandra Marsh. (C). 62 



b 5 "Ripple marks" absent or local; very irreg- 

 ular. Ohio Buckeye, A. glabra Willd. (C). 

 (Plate VI, Figs. 5, 6); California Buckeye, A. 

 calif ornica Nutt, (Ps). 

 b 4 Wood of only moderately fine texture. Pores 

 barely visible to unaided eye; somewhat larger 

 and more numerous in early wood; often in 

 short radial groups. Color light brown tinged 

 with red; surface of freshly cut sapwood soon 

 stained greenish-brown upon exposure. Lustre 

 dull. Pith flecks common. "Ripple marks" 

 absent except possibly over small areas. Wood 

 light, firm, moderately strong; sp. gr. about .48. 

 Growth rings not terminated by parenchyma. 

 Broad rays occasionally present, being aggre- 

 gates of small rays. (Plate V, Figs. 3, 4). 

 Ordinary rays 1-2 cells wide; homogeneous. Vessels 

 without spirals; perforations scalariform, few to many 

 bars; pits into ray cells half-bordered. Wood paren- 

 chyma scanty, diffuse. Red Alder, Alnus oregona 

 Nutt., or A. rubra Bong. (P). 63 

 b 3 Rays indistinct even under lens. 



