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. 

 Co2OT_pjJe_yellow_to nearly jgrhite. 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, JZsculus 

 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. 



