588 TREES OF NORTH AMERICA 



unfold coated with pale tomentum and at maturity glabrous with the exception of the 

 puberulous petiole and rachis; persistent or tardily deciduous; leaflets oblong-linear, obtuse 

 or acute at apex, oblique at base, very short-petiolulate, light green on the upper surface, paler 

 on the lower surface, I '-\' long. Flowers white to violet-yellow, in globose or oblong heads 



Fig. 539 



\' in diameter, on thin pubescent peduncles bracteolate at apex, coated at first, like the 

 flower-buds, with thick white tomentum, developed usually in pairs from the axils of lance- 

 olate acute scarious deciduous bracts, and arranged in short terminal racemes; calyx 

 shortly 5-lobed, puberulous on the outer surface, about gV l n g and one fourth the length of 

 the puberulous petals persistent with the stamens at the base of the mature legume; sta- 

 mens nearly \' long. Fruit ripening at midsummer and often persistent on the branches 

 after opening until the trees flow^er the following year, straight, slightly torulose, short- 

 stalked, contracted at apex into a short slender point, 4'-6' long and f ' wide, its valves thin, 

 thick-margined, reddish brown on the outer surface, yellow tinged with red on the inner 

 surface, reticulate- veined; seeds suspended by a slender coiled and somewhat dilated funi- 

 cle, compressed, ovoid to nearly orbicular, dark chestnut-brown, very lustrous, \' long, and 

 faintly marked by large oval depressions; seed-coat thin, cartilaginous. 



A tree, 25-30 high, with a trunk rarely 5'-6' in diameter, slender upright branches 

 forming a narrow irregular head, and branchlets slightly striately angled, covered with 

 minute white lenticels, light gray and puberulous when they first appear, becoming dark 

 brown in their second year, and armed with stout rigid stipular spines sometimes \' long 

 and persistent for many years; more often a shrub, sometimes only 2-3 tall. Bark of 

 the trunk smooth, light gray somewhat tinged with red, and often marked by large pale 

 blotches. Wood dark-colored, hard, and heavy. 



Distribution. Bluffs and bottom-lands of the lower Rio Grande, and on the upper 

 Nueces River in Uvalde County, Texas; usually a low shrub spreading into broad clumps, 

 but occasionally in the rich and comparatively moist soil of the banks of river-lagoons 

 a slender tree; in Mexico more abundant, and of its largest size from the mouth of the Rio 

 Grande to the Sierra Madre of Nuevo Leon. 



3. Pithecolobium flexicaule Coult. Ebony. 

 Zygia flexicaulis Sudw. 



Leaves persistent, l$'-2' long, 2|'-3' wide, long-petiolate with slender puberulous 

 petioles glandular near the middle and furnished at apex with small orbicular solitary 

 glands, and 4-6 usually 6-foliolate pinnae, the lowest pair often the shortest; leaflets 



