An erect, spreading or more often ascending shrub, usually 60-150 cm high, with old branches usually pale grey, their ends varying from weakly to rather strongly thorn-like. Young branches relatively slender, ascending, glabrous, often longitudinally striate. Leaves of long-shoots supported by a distinct but not very prominent leaf base. Petiole green, flat or usually somewhat U-shaped in transverse section, relatively long: from c. 3 to more than 15 mm, glabrous, often somewhat constricted and pale at the base, persisting for some time after the leaflets have been shed (but not becoming hard and woody). Leaflets oblanceolate, 5-17(-20) x 1.7-5.0(-6.5) mm, glabrous, smooth but with dull surface, weak, somewhat yellowish-green, easily becoming dark when dried (cf. the name “fusca”); apex rounded, obtuse but with a distinct and up to more than 0.5 mm long apicula. Short-shoots only occasionally developed (seldom seen in pressed material), when present with several leaves; these usually with narrow, longitudinally incurved leaflets and with pedicels usually shorter than leaflets. Raceme slender, 5-10(-15) cm long, rather weak, with (10-)30-50 flowers; axis glabrous, slender. Bracts shed when the flowers are in early bud, lanceolate, 1.0-2.5 mm long, acuminate, glabrous. Pedicel very slender, glabrous, (1.5-)1.8-3.2(-3.5) mm long in the flowering stage. Bracteoles persisting somewhat longer than bracts and generally smaller, 0.3-1.2 mm long, subulate to linear or lanceolate, glabrous. Calyx obliquely and openly campanulate, relatively small, glabrous; the upper two lobes 0.5-1.2 mm long, triangular, acuminate, separated by broader sinuses from the more closely spaced lower three; these 0.6-1.2 mm long, somewhat narrower than the upper, the lowest lobe almost subulate. Petals glabrous, generally pale greenish-yellow. Standard blade narrowly ovate or elliptic, 4.6-6.5 x 2.6-4.2 mm, usually broadest near the base, obtuse or subacute and slightly incurved at the apex, at anthesis strongly recurved at the base; claw 2.4-3.7(-4.0) mm long. Wing blades narrowly ovate, 4.6-6.0 x 1.8-3.0 mm, broadest near the base; claws 2.0-3.2(-3.7) mm long. Keel blades somewhat beaked, 4.8-5.8 x (2.1-)2.5-3.5 mm, with upper margina upcurved and apex almost pointed; lateral bulges lacking; claws (1.8-)2.2-3.2 mm long. Pistil glabrous; stipe 2-4 mm long; ovary 4-8-ovulate, with prominent upper wing but without lateral ridges. Fruit an indehiscent, obliquely oval, flat samara, usually 12.5-17.5 x 8.5-12.0 mm, but in certain forms up to 32 x 15 mm, smooth, with visible veins but lacking any reticulately elevated pattern on the sides, often becoming whitish; the upper wing 2.6-4 mm broad and generally reaching considerably beyond the style base apically.
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