Description: Small shrubs, subshrubs or perennial herbs; most species forming a basal rosette, arising from taproots and/or thick caudexes, sometimes with roots that form tuber-like growths.
Leaves alternate, bipinnate, ending in a pair of pinnae plus a single terminal pinna; pinnae opposite, in 1–13 pairs; area of pinnae attachment to the rachis variable, swollen, glabrous and/or with few to several, often capitate, multicellular glandular trichomes or processes that sometimes form a crown-like mass; leaflets 2–15(-18) pairs per pinna, glabrous to pubescent; stipulate.
Inflorescence a terminal or axillary raceme; bracts often caducous. Flowers zygomorphic; sepals 5, persistent in fruit, rachises and sepals with simple trichomes or linear, multicellular glandular trichomes, or both; petals 5, yellow to orange, subequal, clawed; stamens 10, free, filaments pubescent; ovary glabrous to pubescent, eglandular to glandular, stigma apical, concave.
Fruit indehiscent or dehiscent legumes, compressed laterally, straight or sometimes falcate; valves, if dehiscent, curling outward or twisting, glabrous or variously adorned with simple trichomes or multicellular glandular trichomes, or both; seeds compressed, ovoid.
Distribution and occurrence: World: 23 species. Native to North America (southern USA and Mexico) and South America. Australia: 1 species naturalised.
Text by SF McCune
Taxon concept:
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