Habit and leaf form. Trees, or shrubs; evergreen, or deciduous; laticiferous, or non-laticiferous and without coloured juice; resinous. Leaves cauline. Stem internodes solid. Self supporting, or climbing. Leaves alternate; spiral; ‘herbaceous’; petiolate (petiole more or less laterally ridged); flowers fragrant; simple. Leaf blades oblong (oblong-ovate), or obovate (to narrowly obovate or to oblong-obovate); veins prominent; cuneate at the base (narrowly, or decurrent). Leaves without stipules. Leaf blade margins entire. Leaf anatomy. Hairs present. Extra-floral nectaries absent. Stem anatomy. Secondary thickening developing from a conventional cambial ring.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in panicles (usually). The terminal inflorescence unit racemose. Inflorescences terminal, or axillary. Flowers pedicellate (articulate just below the base of the calyx); bracteate (overlapping the base of the calyx); bracteolate (2 per flower); regular; 5 merous; cyclic; tetracyclic, or pentacyclic. Free hypanthium present (short), or absent. Hypogynous disk present; intrastaminal; annular. Perianth with distinct calyx and corolla; 3–5, or 6–10; 1 -whorled, or 2 -whorled; isomerous. Calyx present; (4–)5(–6); 1 -whorled; polysepalous, or gamosepalous; toothed (or ciliate); imbricate; regular. Sepals ovate (broadly; Note: this shape describes the free lobe of the joined calyx). Corolla present; (4–)5(–6); 1 -whorled; polypetalous; imbricate; white, or cream. Petals elliptic, or oblong (oblong-elliptic). Androecial members definite in number. Androecium 6. Androecial members free of the perianth; all equal; free of one another; 1 -whorled, or 2 -whorled. Androecium exclusively of fertile stamens, or including staminodes. Staminodes when present, 1–9. Stamens (8–)10(–12) (twice the number of petals); all more or less similar in shape; round the disc. Anthers basifixed; versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate. Pollen shed as single grains. Gynoecium 4–5 carpelled. The pistil 1 celled. Gynoecium syncarpous (connate only at the base); synovarious; superior (usually). Ovary unilocular; 1 locular. Gynoecium stylate (the single fertile style is reduced). Styles 1 (1 fertile, 3–5 sterile); free; ‘gynobasic’ (having 3–5 sterile carpels whose the prominent stigmas function as gynobasic styles). Stigmas 5 (prominent and sterile, and 1 obsolete and fertile stigma). Placentation parietal, or basal. Ovules in the single cavity 1; pendulous, or ascending; apotropous; with ventral raphe, or with dorsal raphe; non-arillate; anatropous.
Fruit and seed features. Fruit fleshy (scarcely); indehiscent; a drupe; 1 seeded (per cell usually). Seeds non-endospermic. Cotyledons 2. Embryo curved.
Etymology. After Francis Hamilton (ne Buchanan, 1762–1829).