Shrubs, to 1 m. Leaves xero­phytic, first pair of leaflets often caducous, 1.2–3.7 cm, strig­ulose; stipules persistent; extra­floral nectaries 0; leaflet pairs 3 or 4, blades obovate, 4–10 × 2.5–7.5 mm. Racemes 2–17-flowered, not spikelike; bracts caducous, to 5 mm. Pedicels 12–26 mm. Flowers asymmetric, enantiostylous; calyx yellowish, greenish, or purplish brown; corolla bright yellow, highly asymmetric, lower petals strongly concave (flag-shaped), longest petal 16–28 mm; androecium heterantherous, stamens 7, staminodes 3; anthers of middle stamens 4–6.2 mm, of abaxial stamens 4.8–6.2 mm, dehiscing by 2 apical slits, apical appendage 0; gynoecium incurved, ovules 22–25; ovary glabrous; style incurved. Legumes ascending, flat, straight or slightly curved, 70–240 × 5.5–8 mm, corrugated over seeds, tardily dehiscent. Seeds brown to pinkish brown, rhomboid to paddle-shaped.

Phenology: Flowering late spring–mid fall.
Habitat: Foothills of desert mountains.
Elevation: 800–1600 m.

Distribution

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Ariz., N.Mex., Tex., Mexico (Chihuahua, Coahuila, Sonora).

Discussion

Varieties wislizeni and villosa (Britton) H. S. Irwin & Barneby display persistent stipules and the fruits are corrugated over the seeds, whereas stipules are promptly caducous and fruits are not corrugated in vars. pringlei (Rose) H. S. Irwin & Barneby and painteri (Britton) H. S. Irwin & Barneby. Variety villosa and var. wislizeni are distinguished by their vestiture: the former is pilosulous, whereas the latter is strigulose (H. S. Irwin and R. C. Barneby 1982).

Selected References

None.

Lower Taxa

None.