LEGUMINOS&. SILVA OF NORTH AMERICA. 31 
EYSENHARDTIA ORTHOCARPA. 
LEAVES composed of 10 to 23 pairs of leaflets. Legume nearly straight, pendent. 
BKysenhardtia orthocarpa, Watson, Proc. Am. Acad. xvii. HE. amorphoides, var. orthocarpa, Gray, Smithsonian 
339. — Sargent, Forest Trees N. Am. 10th Census U. S. Contrib. v. 37 (Pl. Wright. ii). 
ix. 55. — Coulter, Contrid. U. S. Nat. Herb. ii. 76 (Man. EH. amorphoides, Torrey, Bot. Mex. Bound. Surv. 51 (in 
Pl. W. Texas). part). 
A small tree, occasionally eighteen or twenty feet in height, with a trunk six or eight inches 
in diameter, separating, three or four feet above the ground, into a number of slender branches; or 
more often a low rigid shrub. The bark of the trunk is a sixteenth of an inch thick, light gray, and 
broken into large plate-like scales, their surface exfoliating in thin layers. The branchlets are at first 
coated with ashy gray pubescence ; this disappears during the second year, when they are reddish brown 
and roughened with numerous glandular excrescences. The leaves are four or five inches long, with 
pubescent midribs grooved on the upper side, ten to twenty-three pairs of leaflets, and small scarious 
deciduous stipules. The leaflets are oval, rounded or sometimes slightly emarginate at the apex, with 
stout petiolules and minute scarious deciduous stipels, and are furnished on the lower side with con- 
spicuous chestnut-brown glands; they are pale gray-green, glabrous or slightly puberulous on the 
upper surface, pubescent below, especially along the prominent midrib, reticulate-veined, and conspicu- 
ously glandular-punctate, with thickened slightly revolute margins, and vary from half to two thirds of 
an inch in length and from an eighth to a quarter of an inch in breadth. The flowers are produced 
in May in axillary pubescent spikes three or four inches long; they are borne on slender pubescent 
pedicels and are rather less than half an inch long. The calyx is many-ribbed, pubescent, covered with 
large and conspicuous glands, and half the length of the white petals, which vary little in size and shape 
and are ciliate on their margins. The legume is half an inch long, pendent, nearly straight or slightly 
falcate, conspicuously thickened on the two edges, and usually contains a single seed near the apex. 
Eysenhardtia orthocarpa is found from the valley of the upper Guadaloupe River in western 
Texas to the Santa Catalina and Santa Rita mountains of southern Arizona, and extends southward 
into Mexico to the neighborhood of San Luis Potosi and to southwestern Chihuahua. It grows in 
gravelly soil on arid slopes and dry ridges, and is only known to assume an arborescent form near the 
summit of the Santa Catalina Mountains. 
The wood of Hysenhardtia orthocarpa is heavy, hard, and close-grained, with numerous rows of 
open ducts clearly marking the layers of annual growth, and many thin medullary rays. It is light 
reddish brown in color, with thin clear yellow sapwood composed of seven or eight layers of annual 
growth. The specific gravity of the absolutely dry wood is 0.8740, a cubic foot weighing 54.47 
pounds. 
Eysenhardtia orthocarpa was discovered by Charles Wright’ in August, 1849, on the banks of a 
stream between the Pecos and Limpia rivers in western Texas. 
1 See i. 94. 
