780 The Bumelias 



5. ARIZONA BUCKTHORN — BumeUa rigida (A. Gray) SmaU 

 Bumelia lanuginosa rigida A. Gray 



A small tree occurring along streams from western Texas to Arizona and 

 adjacent Mexico, reaching a maximum height of 7.5 meters. 



The trunk is short, its branches are stifiF, spreading and very spiny. The bark 



is fissured into long, flaky red- 

 brown ridges. The twigs are 

 stout, rough and dark gray. The 

 leaves are thick and leathery, 

 varying from wedge-shaped to 

 nearly oblong, 1.5 to 3 cm. long, 

 rounded or notched at the apex, 

 gradually or abruptly tapering at 

 the base, somewhat revolute on 

 the margin, dark green and 

 smooth above, woolly beneath, 

 the leaf-stalk i to 3 mm. long. 

 The flowers are in rather few- 

 flowered fascicles, on pedicels 4 



to 8 mm. long; the calyx-lobes 

 Fig. 711. — Arizona Buckthorn. 11.1 1 



are suborbicular, 2 mm. long, 



the corolla-lobes suborbicular, 2 mm. broad and irregularly toothed, the ap- 

 pendages lanceolate to ovate-lanceolate and sharp-pointed; staminodes ovate-lan- 

 ceolate, irregularly toothed and blunt; stamens shorter than the corolla; ovary 

 hairy. The fruit is oblong-oval or oval, 10 to 12 mm. long, black, often tipped 

 with the persistent style. 



The wood is hard, very close-grained, light brown, sometimes yellowish; its 

 specific gravity is about 0.66. 



6. Woolly buckthorn— BumeUa lanuginosa (Michaux)Persoon 

 Sideroxylon lanuginosum Michaux 



This, the largest species of its genus, grows in sandy woods and thickets 

 from southern Illinois and Kansas to Georgia, northern Florida and Texas; it 

 reaches its greatest size, 20 meters tall, with a trunk diameter up to i m., in eastern 

 Texas, but is usually much smaller and sometimes shrubby. It is also called 

 Gum elastic. Black haw, Shittimwood, and Chittimwood. 



The trunk is straight, its branches short, straight, and stiff. The bark is 

 about 12 mm. thick, deeply fissured in both directions into scaly ridges of a dark 

 grayish brown color. The twigs, covered with thick brownish wool at first, 

 become nearly smooth; they are brown to gray and often bear stout, stiff, 



