1. Annual or perennial herbs............................................................................................................................................. 2

- Trees, shrubs or lianas................................................................................................................................................... 4

2. Flowers 4-merous, solitary or inflorescences few-flowered, branches up to 25 cm long; leaves usually with a single vein or 1−3-veined................................................................................................ Mitrasacme Labillardière (1805: 35)

- Flowers 5-merous, inflorescences many-flowered, pedunculate, branched or unbranched to 15 cm long; leaves pinnately veined............................................................................................................................................................ 3

3. Inflorescences branched, not subtended by a pseudowhorl of leaves, leaves petiolate; corolla 2−3 mm long, ovary semi-inferior...................................................................................................................................................... Mitreola

- Inflorescences unbranched, subtended by a pseudowhorl of four subsessile leaves; corolla 6−7 mm long, ovary superior.............................................................................................................................................................. Spigelia

4. Leaves 3−5(−7)-pliveined (with one or a few pairs of strongly developed basal nerves in addition to the midrib); axillary tendrils and/or axillary thorns often present................................................... Strychnos Linnaeus (1753: 189)

- Leaves pinnately veined; tendrils and thorns absent.................................................................................................... 5

5. Inflorescences terminal, sometimes also axillary in axils of upper pair of reduced leaves; flowers 5-merous; fruit capsular with few to many small, slender seeds.............................................................. Norrisia Gardner (1849: 326)

- Inflorescences axillary; flowers 4−5-merous (4-merous in Peninsular Malaysia); fruit a berry with 1−2 orbicular seeds (in Peninsular Malaysia)....................................................................................................................... Gardneria