Xi Shu

Camptotheca acuminata Decne. (Nyssaceae), the happy tree or cancer tree, is a fast-growing deciduous broadleaved tree reaching 20-25 m in height, endemic to southern China and Tibet. The trunk is straight with smooth grey bark; young branches are reddish-green and glabrous. Leaves are opposite, ovate to elliptic-oblong, 12-28 cm long, with entire margins, an abruptly acuminate tip, and prominent pinnate venation, glossy dark green above and lighter beneath with pubescent veins. The inflorescence is a globular head 1.5-2 cm in diameter consisting of many small greenish-white flowers, the heads arranged in axillary or terminal clusters, with separate male, female, and bisexual heads on the same tree. The fruit is a narrow winged samara 2-2.5 cm long, brown at maturity, aggregated into pendulous heads. The tree is the original natural source of camptothecin and its derivatives (irinotecan, topotecan), used in TCM and modern oncology for cancer treatment.