Yun Shi

Yun Shi is generally identified as the seed of Caesalpinia decapetala (Roth) Alston (Fabaceae), a vigorous, prickly scrambling shrub or liana native to southern and central China, India, and Southeast Asia. The plant produces bipinnate leaves with small, oblong leaflets and showy racemes of yellow, five-petaled flowers in spring and early summer. The fruit is a flat, woody, oblong-oblanceolate pod 6–12 cm long that splits at maturity to release 4–9 hard, smooth, dark brown to black seeds 8–12 mm across. Stems and rachises bear stout, recurved prickles. In Chinese materia medica the seeds are harvested in autumn, dried, and used in decoction for clearing damp-heat and dispelling parasites; identification of “Yun Shi” in older texts is variable, so verify source before clinical use.