40. Keenania J. D. Hooker, Fl. Brit. India. 3: 101. 1880.
溪楠属 xi nan shu
Authors: Tao Chen & Charlotte M. Taylor
Herbs or subshrubs, unarmed. Raphides apparently present. Leaves opposite, perhaps without domatia; stipules caducous or usually persistent, interpetiolar, triangular, usually aristate, sometimes somewhat inflated. Inflorescences terminal or sometimes pseudoaxillary, capitate, several to many flowered, pedunculate, bracteate with basalmost bracts usually involucrate and remaining bracts often well developed and paired. Flowers sessile, presumably bisexual, biology unknown. Calyx limb 4-, 5-, or sometimes 6-lobed with lobes sometimes unequal, sometimes imbricate in bud, sometimes gland-tipped. Corolla white or yellow, funnelform with tube sometimes inflated, inside pubescent in upper part and throat; lobes 4, 5, or sometimes 6, ovate and acuminate, valvate in bud. Stamens 5, inserted at corolla base, included or partially exserted; filaments short to developed; anthers dorsifixed near base. Ovary 2-celled, ovules numerous in each cell on globose, peltate, axile placentas; stigma 2-lobed, included or exserted. Fruit unknown.
About five species: Cambodia, S China, India, Laos, Myanmar, Thailand, Vietnam; two species (one endemic) in China.
This genus is not well known or documented. Puff et al. (Rubiaceae of Thailand, 180. 2005) described the flowers as "unisexual (?)," though they did not say whether the plants are dioecious, and suggested that the fruit of Keenania will eventually be found to be capsular. The absence of raphides was implied by the placement of this genus in the Isertieae in FRPS (71(1): xiii. 1999), but raphides are clearly evident on specimens referred to K. ophiorrhizoides Drake from Vietnam (MO!) and thus are provisionally cited for the genus.