Vincetoxicum, Wolf (1776: 130), Wolf, 1776

Hsu, Tian-Chuan, Huang, Wei-Jie & Chung, Shih-Wen, 2021, Vincetoxicum (Apocynaceae: Asclepiadoideae) in Taiwan: Two new combinations and a new record, Phytotaxa 478 (2), pp. 287-290 : 287

A key to the species is also provided as below to aid their identification.

1. Stems erect; peduncles shorter than 1 cm .......................................................................................................... Vincetoxicum atratum

- Stems twining or prostrate; peduncles longer than 2 cm ...................................................................................................................2.

2. Stems prostrate; leaves nearly orbicular.................................................................................................................... Vincetoxicum sui

- Stems twining; leaves linear-lanceolate to ovate...............................................................................................................................3.

3. Corolla lobes oblong-lanceolate, 6–10 mm long...............................................................................................................................4.

- Corolla lobes ovate, 2–4 mm long.....................................................................................................................................................5.

4. Stems puberulent along two lines; leaves sparsely puberulent on main veins and along margin, otherwise glabrous; corolla yellow-white ..................................................................................................................................................................... Vincetoxicum fordii

- Stems and leaves uniformly pubescent; corolla purple or at least purplish at base ................................... Vincetoxicum mooreanum

5. Leaves obtuse to rounded at base, subtrinerved; calyx with 5 colleters inside ................................................ Vincetoxicum oshimae

- Leaves rounded to subcorded at base, pinnately veined; calyx without colleters .............................................................................6.

6. Plant glabrous except for very young stems................................................................................................ Vincetoxicum taiwanense

- Plants variously hairy ........................................................................................................................................................................7.

7. Leaves lanceolate, 0.8–2.1 cm wide, usually> 3× as long as broad.................................................................................................8.

- Leaves ovate, 1.5–4.0 cm wide, usually <3× as long as broad.........................................................................................................9.

8. Peduncles and pedicels pubescent ................................................................................................................. Vincetoxicum insulicola

- Peduncles and pedicels glabrous ............................................................................................................................... Vincetoxicum lui

9. Stems densely pubescent; leaves pubescent on both surfaces......................................................................... Vincetoxicum hirsutum

- Stems sparsely pubescent; leaves glabrescent................................................................................................... Vincetoxicum brownii