2n = 18

n = 9 bivalents

Bushy, spreading to decumbent shrub, up to 3 m high, with several prostrate, decumbent and/or spreading main branches arising at or near ground level. Divaricating and/or flexuose juvenile branchlets absent; branchlets prostrate, decumbent to spreading, moderately to densely pubescent, becoming glabrous with age; hairs appressed, straight. Seedlings and juveniles moderately to densely leafy, leaves with increasing numbers of leaflets. Leaflets of juveniles 2.5-3.5 × 2.0-2.5 mm, rotund to broadly elliptic, sparsely to moderately hairy, not crowded or overlapping. Leaves on adults up to 10 cm long, imparipinnate, subconduplicate, petioles and rachides channelled above, leaflets 23-37. Leaflets on adults 5.0-12.0 × 2.0-6.0 mm, elliptic, elliptic oblong, to broadly elliptic, distal and proximal leaflets similar in size, not crowded or overlapping, distant, adaxial surface dark green, abaxial surface light green; apices round to slightly retuse; bases obtuse; petiolules 0.4-0.5 mm long; petioles, rachides, petiolules, and leaflets usually pubescent, hairs c. 0.2 mm long, appressed, straight. Inflorescences racemose, with up to 5 flowers, flowers usually hidden among foliage; peduncles and rachides 10- 20 mm long; Pedicels up to 15 mm long, each subtended by a bract; bracts 1-2 mm long; peduncles, rachides, pedicels, bracts, and calyces moderately to densely pubescent, hairs brown, appressed. Calyx 9-12 × 10-16 mm, cupulate, rim shallowly lobed, with deeper notch adjacent to standard. Corolla yellow; keel petal blade 26-30 × 7.5-11 mm; wing petal blade 25-30 × 6.5-8.5 mm; standard petal blade 20-23 × 18-21 mm; petals with distinct claws, 4.5-7.5 mm long. Stipe 5-7 mm long, glabrous to sparsely pubescent. Ovary 18-20 mm long, densely pubescent; hairs 0.2-0.4 mm long, off- white to light brown, appressed. Style 11-12 mm long, glabrous to sparsely pubescent. Stigma fringed with short hairs. Filaments 24-30 mm long. Anthers 1.7-2.1 × 0.8-0.9 mm. Fruit 50-100 mm long 4- winged, brown, sparsely to moderately pubescent, with up to 9 seeds. Seeds 4.3-8.8 × 3.0-4.0 mm, oblong, light brown to yellow. FL Apr-Oct; FT Jun- May.

A S. microphylla differt ramificatione juvenili non divaricata, facie compacta fruticosa saepe decumbenti, foliis atroventribus subanthesi noncaducis et interea floribus plerumque sparsim dispositis, et in habitatione in scopulis expositis.