ECONOMIC WOODS OF THE UNITED STATES 91 



streaks showing on longitudinal surface. 

 Lustre high. Very small pin knots due to 

 thorns common. Wood usually knotty and 

 cross-grained, without worm holes. Osage 

 Orange, Toxylon pomiferum Raf., or Madura 

 aurantiaca Nutt., (C, S). Plate III (Fig. 4). 36 



b 5 Color varying from golden-yellow to brown, 

 often greenish in young trees; usually uni- 

 form in same specimen ; not striped with red. 

 Lustre not so high as in preceding; wood 

 mostly straighter-grained and freer from 

 knots. Large worm holes common. Black 

 or Yellow Locust, Robinia pseudacacia L. 

 (C, A). Plate III (Fig. 3). 37 



b 3 Tyloses absent or rare, not light-colored; dark- 

 colored gum deposits present. 



a* Wood parenchyma conspicuous in numerous 

 very irregular tangential bands which include 

 the pores. Pores in late wood varying in size 

 from minute to as large sometimes as in early 

 wood; arrangement very irregular. Dark red 

 gum deposits in vessels conspicuous, showing as 

 dark wavy lines on tangential surface. Wood 

 dull mahogany color; thin sapwood greenish 

 yellow. Sp. gr. .77. Vessels without spirals; per- 

 forations simple; pits into ray cells half-bordered. Rays 

 homogeneous. Mesquite or Algaroba, Prosopis 

 juliflora (Schwartz) de C. (Rs). 38 



b 4 Wood parenchyma mostly in patches about the 

 pores in late wood, sometimes confluent in 

 outer portion. Pores in outer portion of growth 

 ring all very small; distribution fairly regular. 

 Gum deposits usually inconspicuous. Sp. gr. 

 .67-.70. Small vessels with spirals; perforations simple; 

 pits into ray cells half-bordered. Rays mostly homoge- 

 neous. 



a 5 Pores in outer portion of late wood usually 

 in groups of 5-20; individual pores visible 

 under lens. Sapwood thin. Texture very 



