Description from Flora of China
Schetti Adanson; Tsiangia But, H. H. Hsue & P. T. Li.
Shrubs or small trees or occasionally perhaps climbing (Ixora hekouensis), unarmed. Raphides absent. Leaves opposite or rarely ternate, decussate, without domatia; petioles articulate at base; stipules persistent to caducous, interpetiolar or shortly united around stem, triangular, acute to usually aristate. Inflorescences terminal on principal stems [or sometimes terminal on reduced lateral stems and appearing axillary], cymose to corymbiform or paniculiform, few to many flowered, sessile to pedunculate, bracteate or bracts reduced; axes often articulate; bracteoles when present often fused in pairs. Flowers pedicellate or sessile, bisexual, monomorphic, often fragrant. Calyx limb truncate or 4-lobed. Corolla yellow, orange, red, or white, sometimes becoming reddened when dry, salverform with tube slender, inside glabrous or pubescent at throat; lobes 4 [rarely to 9], convolute in bud. Stamens 4, inserted at corolla throat, partially to fully exserted; filaments short or reduced; anthers dorsifixed near base. Ovary 2-celled, ovules 1 in each cell, pendulous from axile placentas attached in upper part of septum; style in upper portion fusiform or clavate; stigmas 2, linear, recurved, exserted. Fruit black or red, drupaceous, leathery or fleshy, subglobose to ellipsoid or ovoid, with calyx limb persistent; pyrenes 2, 1-celled, each with 1 seed, plano-convex or concavo-concave, smooth dorsally (i.e., abaxially), leathery, papery, or crustaceous; seeds medium-sized, ellipsoid to oblanceolate, grooved and concave ventrally (i.e., adaxially); testa membranous; endosperm cartilaginous; radicle terete, hypogeous.
Ixora has been studied in SE Asia only by Bremekamp; he published several articles treating the species of several regions there (cited by De Block, Opera Bot. Belg. 9: 213. 1998) but not specifically treating the Chinese species, although his circumscription of the region "Burma and the Andaman Islands" included some species from Xizang (Bremekamp, J. Bot. (London) 75: 108-111, 169-175, 260-266, 295-298, 318-326. 1937).
Several species of Ixora are widely cultivated in tropical regions as ornamentals, notably I. casei Hance, I. coccinea Linnaeus, I. finlaysoniana, and sometimes I. chinensis. In cultivation several of these have various forms with a wide range of flower color, flower and leaf size, and plant height, and sometimes they do not set fruit. Ixora coccinea and I. casei are not treated in this current flora but are included in the key to species below for identification. Reynolds and Forster (Austrobaileya 7(2): 253-278. 2006) reported that I. coccinea is locally adventive in some parts of Australia, which may be a possibility in China. The most commonly cultivated Ixora species were discussed in detail by Fosberg and Sachet (Baileya 23(2): 74-85. 1989).
Ixora foonchewii was described and illustrated as having consistently 5 corolla lobes and a stout, shortly bilobed stigma, so it does not seem to belong to Ixora; it is provisionally included here in Tarenna.
About 300-400 species: widespread in tropical Africa, America, Asia, Madagascar, and Pacific islands; 18 species (nine endemic) in China.
(Authors: Chen Tao (陈涛); Charlotte M. Taylor)