Description from Flora of China
Herbs annual or perennial. Stem erect or climbing by means of tendrils, winged or wingless. Leaves paripinnate, with rachis terminating in a branched or simple tendril or a bristle, rarely phyllodic or reduced to modified stipules; stipules sagittate or semisagittate, usually smaller than leaflets, sometimes large and leaflike; leaflets 1- to many paired, elliptic, ovate, ovate-oblong, lanceolate, or linear; veins parallel, pinnate, or reticulate. Inflorescence an axillary, pedunculate, 1- to many flowered raceme. Calyx campanulate, unequally or equally toothed; teeth not leaflike, at least 2 teeth less than 2 × as long as tube. Corolla purple, pink, yellow, or white, sometimes crimson, brick red, or orange. Staminal tube not oblique at apex; filaments filiform or distally dilated. Style linear or distally dilated, dorsally compressed, pubescent on upper side. Legume laterally compressed, dehiscent. Seeds 2 to many.
The yellow-flowered species of SE China are a particularly difficult and poorly understood group, represented by only limited gatherings.
About 160 species: mainly in Asia, Europe, and North America, with some South American endemics; 18 species (three endemic, three introduced) in China.
(Authors: Bao Bojian (包伯坚); Gregory Kenicer)