Acmena Candolle; Caryophyllus Linnaeus (1753), not Miller (1754); Cleistocalyx Blume; Jambosa Adanson, nom. cons.

Trees or shrubs. Branchlets sometimes 2-4-ridged, usually glabrous. Leaves opposite or sometimes whorled, petiolate to subsessile; leaf blade densely to sometimes sparsely pinnately veined. Inflorescences terminal or axillary, usually panicles of cymes, 3- to many-flowered; bracts small, caducous after flowering. Flowers stipitate or not. Hypanthium obconic or sometimes clavate. Calyx lobes 4 or 5 or rarely more, usually short, caducous or persistent, apex usually obtuse, rarely connate and then calyptrate. Petals 4 or 5 or rarely more, distinct and then expanding separately or coherent and then caducous as a unit. Stamens numerous, distinct but occasionally slightly adhering at base; anthers minute, versatile, 2-celled, cells parallel or divergent, dehiscing longitudinally or by a short terminal slit; connectives usually terminating in an apical gland. Ovary inferior, 2 or 3-loculed; ovules many per locule. Style linear. Fruit drupaceous, 1(or 2)-seeded. Seeds sometimes with or without a testa, often with a pseudotesta ± adhering to pericarp, rarely with intrusive branching tissue extending into and interlocking cotyledons; embryo usually uniembryonic, sometimes polyembryonic.

Syzygium is treated here in a broad sense with Acmena and Cleistocalyx included within it. Morphological and anatomical investigations, and molecular sequence studies of chloroplast and nuclear regions, provide support for such an expanded concept (Amer. J. Bot. 59: 423-436. 1972; Bot. Jahrb. Syst. 92: 433-489. 1972; Proc. Fourth Fl. Mal. Symp. 75-85. 2001; Austral. Syst. Bot. 17: 63-72. 2004; Taxon 55: 79-94. 2006).

In addition to the cultivated species treated here, both Syzygium aqueum (N. L. Burman) Alston (Eugenia aquea N. L. Burman) and S. grande (Wight) Walpers (E. grandis Wight) have been recorded as being cultivated in China.

Flowers are not known in Syzygium album, S. buxifolioideum, S. guangxiense, S. hainanense, S. jienfunicum, S. lasianthifolium, S. melanophyllum, and S. wenshanense.

Fruit are not known in Syzygium bubengense, S. cathayense, S. gongshanense, S. infrarubiginosum, S. laosense var. quocense, S. paucivenium, S. rockii, S. saxatile, S. sichuanense, and S. xizangense.

About 1200 species: tropical Africa, subtropical to tropical Asia, Australia, New Caledonia, New Zealand, Pacific islands; 80 species (45 endemic, two introduced) in China.