524 



The Acacias 



late, 3 mm. long, united at the base, woolly margined ; stamens numerous, about 6 

 mm. long; ovary stalked and hairy. The fruit is flat, linear-oblong, 8 to 12 cm. 

 long, 1.5 to 2 cm. wide, much curved and contorted, and constricted between the 

 seeds, usually rounded at the apex, obliquely tapering into a short stalk, light 

 brown and thick margined, its valves membranous and transversely veined; the 

 seeds are oval-orbicular, 6 mm. in diameter, dark brown, shining, with an oval 

 depression on each side. 



The wood is hard, strong, durable, reddish brown; its specific gravity is about 

 0.85. 



It exudes a gum very much like gum arabic, and locally used as such, but not 

 an article of commerce. 



3. RIO GRANDE ACACIA— Acacia subtortuosa Shafer, new species. 



A small tree, or more often a roimd-topped shrub i to 2 meters high, occurring 

 in the Rio Grande region of southwestern Texas and adjacent Mexico, where it 



attains a maximum height of 6 meters, with a 

 trunk diameter of 1.5 dm. 



The trunk is short, with spreading 

 branches. The bark is deeply fissured and 

 dark brown. The twigs are hairy when 

 yoimg, becoming smooth and dark brown, 

 bearing many whitish spines 2 cm. long or 

 less. The leaves are equally bipinnate, 3 to 

 4 cm. long, including the short leaf-stalk, and 

 composed of 3 or 4 pairs of pinnae, each bear- 

 ing 9 to 14 pairs of leaflets; these are linear, 

 slightly curved, i to 2 mm. long, blunt or mi- 

 nutely tipped at the apex, nearly sessile, light 

 green and smooth or somewhat hairy. The 

 flowers are fragrant and bright yellow, appear- 

 ing in March, in axillary clusters of i to 3 

 globular heads, i cm. in diameter, on slender 

 peduncles 1.5 to 3 cm. long; calyx short, 

 slightly hairy, one third as long as the corolla, 

 the stamens much longer than the corolla. The fruit is long-linear, 8 to 15 cm. 

 long, 6 mm. broad, little flattened, reddish brown, finely hairy, and a little con- 

 stricted between the many seeds, which are obovate, slightly compressed, 6 mm. 

 long, nearly black, with a light brown obovate ring on each side. 



This species has been confused with the similar A . tortuosa (Lirmaeus) Willde- 

 now, of the West Indies. The type specimens were collected by Dr. E. Palmer, 

 near Durango, Mexico, April and November, 1896, Nos. 11 and 510. 



Fig. 485. — Rio Grande Acacia. 



