An Xi Xiang

Styrax tonkinensis is a small to medium evergreen tree in the family Styracaceae, native to montane forests of southern China (Yunnan, Guangxi), Laos, Vietnam, and northern Thailand, growing 10–20 m tall with a slender trunk, smooth grey bark, and alternate ovate-elliptic leaves 5–10 cm long with whitish stellate-tomentose undersurfaces. Pendulous panicles of small fragrant white five-lobed flowers appear in spring, followed by globose drupes about 1 cm across with stellate hairs. The medicinal substance, Siam benzoin, is the balsamic resin obtained by tapping the trunk: V-shaped or triangular incisions are made through the bark in the rainy season, and the milky exudate hardens on exposure to air into yellow-brown to reddish-brown irregular tears and lumps with a vanilla-like aroma. In traditional Chinese medicine An Xi Xiang is acrid, bitter, and neutral, opening the orifices and reviving the spirit in sudden loss of consciousness from cold-phlegm or stroke patterns, and invigorating the blood to relieve chest and abdominal pain from blood stasis.