Chionanthus, Linnaeus, 1753

Quang, Bui Hong & Nuraliev, Maxim S., 2021, The genus Chionanthus (Oleaceae) in Cambodia, Laos and Vietnam, Phytotaxa 525 (3), pp. 167-195 : 169

Key to the species of Chionanthus in Cambodia, Laos and Vietnam

1. Leaves apparently verticillate (some nodes closely spaced) ........................................................................................... C. robinsonii

- Leaves distant .....................................................................................................................................................................................2

2. Leaf blade linear............................................................................................................................................................. C. harmandii

- Leaf blade elliptic, oblong-elliptic, ovate-elliptic, lanceolate or oblanceolate...................................................................................3

3. Inflorescence subcapitate or capitate, flowers subsessile or sessile............................................................................ C. subcapitatus

- Inflorescence paniculate, flowers sessile to distinctly pedicellate .....................................................................................................4

4. Leaf blade 16–33(40) cm long; fruit 5–10 cm long, 2.5–5 cm wide.............................................................................. C. henryanus

- Leaf blade 5–30 cm long; fruit 1–3.5 cm long, 0.5–3 cm wide (unknown in C. macrothyrsus and C. maxwellii ) ...........................5

5. Corolla lobes (6)7–9(10) mm long; leaf blade with 9–11 pairs of secondary veins; inflorescence many-flowered............................ ......................................................................................................................................................... C. mala-elengi subsp. terniflorus

- Corolla lobes 1.5–9 mm long; if lobes longer than 7 mm ( C. maxwellii and rarely C. microstigma ), then either leaf blade with 5–10 pairs of secondary veins, or inflorescence ca. 7-flowered..................................................................................................................6

6. Inflorescence 2.5–20(25) cm long, most often more than 50-flowered; corolla lobes 2–4(5.5) mm long.........................................7

- Inflorescence usually 1–5 cm long (but to 8 cm long in C. hainanensis ), few- to many-flowered; corolla lobes 1.5–9 mm long ..... ............................................................................................................................................................................................................9

7. Leaf blade usually oblanceolate (to oblong-elliptic or elliptic); inflorescence usually 4–10 cm long................................ C. thorelii

- Leaf blade usually oblong-elliptic to ovate-elliptic (rarely lanceolate or oblanceolate); inflorescence usually 2.5–20(25) cm long. ............................................................................................................................................................................................................8

8. Peduncle 1.5–3.3 cm long .............................................................................................................................................. C. ramiflorus

- Peduncle 3.5–6 cm long ............................................................................................................................................ C. macrothyrsus

9(6). Corolla lobes 1.5–3 mm long ...........................................................................................................................................................10

- Corolla lobes 4–9 mm long ..............................................................................................................................................................11

10. Leaf blade with 12–20 pairs of secondary veins; inflorescence densely paniculate, 1–4 cm long; corolla lobes 1.5–2 mm long ...... ...................................................................................................................................................................................... C. microbotrys

- Leaf blade with 7–8 pairs of secondary veins; inflorescence laxly paniculate, 2–8 cm long; corolla lobes ca. 3 mm long................ ...................................................................................................................................................................................... C. hainanensis

11(9). Petiole 1–5 mm long; inflorescence 1–2 cm long; corolla lobes 4–7 mm long ............................................................ C. parkinsonii

- Petiole 5–40 mm long; inflorescence 2–5 cm long; corolla lobes 4–9 mm long .............................................................................12

12. Petiole 5–12 mm long; leaf blade (5) 6–11 cm long; corolla lobes 4–9 mm long ....................................................... C. microstigma

- Petiole 20–40 mm long; leaf blade 11–18 cm long; corolla lobes 7–8.5 mm long ......................................................... C. maxwellii