山扁豆 shan bian dou

Cassia mimosoides Linnaeus, Sp. Pl. 1: 379. 1753.

Herbs, suffrutescent, annual or perennial, with woody base, 30-60 cm tall, or low shrubs to 1 m tall, with many slen­der, puberulent branches. Leaves 4-8 cm, with an orbicular, dis­coid, sessile gland in upper part of petiole, below lowest pair of leaflets; stipules persistent, linear-subulate, 4-7 mm, with con­spicuous longitudinal veins; rachis not canaliculate, sparsely pubescent; leaflets sessile, 20-50(-80) pairs, reddish brown when dry, linear-falcate, 3-4 × ca. 1 mm, midvein near upper margin of blade, very unequally sided, base obliquely truncate, apex acute, mucronate. Flowers supra-axillary, mostly solitary, sometimes 2 or 3 together in a very short raceme; bracts and bracteoles similar to stipules but latter smaller. Sepals lanceo­late, 4-8 mm, apex acute. Petals bright yellow, unequal, obo­vate to orbicular, equal to or slightly longer than sepals, shortly clawed. Stamens 10, alternately 5 shorter and 5 longer; anthers opening by apical pores. Ovary with stiff, appressed hairs; stig­ma flat. Legume flat, falcate, 2.5-5 × ca. 0.5 cm. Seeds 10-20, flat, smooth. 2n = 16.

Slopes, wastelands, among bushes, grasslands. S China [native to tropical America; widely introduced in the tropics and subtropics].

This is a drought-enduring and barren-resistant plant, grown for improving the soil. The roots are used medicinally for treating dysentery.