海岸桐 hai an tong

Small trees, 3-8 m tall; bark becoming black, smooth or often lenticellate; branchlets rather stout, densely strigillose to velutinous-tomentulose usually becoming glabrescent. Petiole stout, 1.5-5 cm, densely strigillose or velutinous; leaf blade drying thinly to stiffly papery, broadly obovate or broadly elliptic, 11-20 × 8-18 cm, adaxially glabrescent, usually shiny, and often rugulose, abaxially densely tomentulose or strigillose to glabrescent, base obtuse, rounded, subcordate, or shortly cordate, apex obtuse or rounded sometimes with a short tip 3-5 mm; secondary veins 7-11 pairs, weakly but regularly looping to connect; stipules ovate or lanceolate, 6-11 mm, moderately to densely strigillose to strigose sometimes becoming glabrescent, obtuse to rounded. Inflorescences produced in with or often below leaves, subcapitate to congested-cymose, densely velutinous-tomentulose; peduncles 3-12 cm; branched portion 1.5-3 × 2-3.5 cm, axes scorpioid; bracts ovate, 5-7 mm, caducous. Flowers sessile. Calyx densely velutinous-tomentulose to strigillose; ovary portion obconic to cupulate, 2-2.5 mm; limb tubular, 2-3.5 mm, truncate. Corolla white, outside densely velutinous-tomentulose to strigillose; tube 2.5-3 cm, inside glabrous except sericeous in throat; lobes 7 or 8, obovate, 8-10 mm, obtuse to rounded. Drupes apparently green at maturity, oblate, 2-3 cm in diam., sparsely strigillose or tomentulose to eventually glabrescent; pyrene included in fibrous mesocarp. Fl. Apr-Jul.

Thickets on sandy and limestone coasts; sea level to near sea level. Guangdong, Hainan, Taiwan [Borneo, India, Indonesia, Japan, Malaysia, Philippines, Singapore, Sri Lanka, Thailand; coastal E Africa, Australia, Madagascar, Pacific islands].

The flowers are nocturnal and open for only one night (Puff et al., Rubiaceae of Thailand, 130. 2005). The fruit of this species float and are dispersed by water, and apparently they are green when mature. This species is known to be distylous in Polynesia and E Africa (Bridson & Verdcourt, Fl. Trop. E. Africa, Rub. (Pt. 2), 416. 1988).