ECONOMIC WOODS OF THE UNITED STATES 93 



a^ Wood parenchyma about pores in late wood and often 

 extending wing-like from them; may become confluent 

 into irregular tangential or concentric lines, especially 

 near outer margin of wide growth rings; parenchyma 

 also terminal. Pores in late wood all much smaller 

 than those in early wood; the latter usually in a rather 

 broad zone, 3-10 pores wide (rarely 1-2). Rays 

 scarcely distinct without lens. Vessels without spirals; 

 perforations simple; pits into ray cells half -bordered. Rays homo- 

 geneous. Terminal parenchyma thick-walled, abundantly and 

 irregularly pitted. Asn. 



a- Pores in late wood rarely joined by wood paren- 

 chyma. Wood of medium hardness and strength. 



a^ Pores in late wood isolated, few, large; in early 

 wood in very broad zone, often over one-half 

 width of ring. Wood comparatively Hght and 

 soft; sp. gr. .47. Color decidedly brown. Ray 

 cells small. Black or Brown Ash. F. nigra Marsh. 

 (C, N) (Plate V, Fig. 2). 



b^ Pores in late wood in radial groups of 2-5, and near 

 outer margin of growth ring somewhat tangen- 

 tially grouped; in early wood in zone of medium 

 width, usually less than one-third of ring. Color 

 light brown, often with reddish tinge. Wood 

 moderately hard and strong. Sp. gr. .57. Ray 

 ceUs large. Oregon Ash, F. oregona Nutt. (P). 



b^ Pores in late wood usually joined tangentially by 

 wood parenchyma. Wood mostly very hard and 

 strong, sp. gr. .63-.72. Color gray-brown, often 

 with reddish tinge; sapwood white. 



a? Pores in early wood in rather broad zone; nu- 

 merous. 



* The specific determination of the ash woods is often difficult or impossible. 

 Lumbermen usually recognize two kinds, namely, white and brown. These 

 two unequal groups are readily distinguishable by their gross features, bome 

 of the wood from southern swamp-grown trees has the structure of white ash 

 but is very light, soft and brash; sp. gr. .38. It is sometimes called punk 

 ash" or "soft ash." 



