Vincetoxicum, Wolf, 1776

Zhang, Cai-Fei, Wang, Yan, Chen, Feng, Zhou, Hou-Lin, Liao, Miao, Odago, Wyclif Ochieng, Hu, Guang-Wan & Wang, Qing-Feng, 2022, Vincetoxicum pingtaoanum (Apocynaceae: Asclepiadeae), a new species from the Three Gorges District in Central China, Phytotaxa 564 (1), pp. 59-70 : 67-68

Key to the species of Vincetoxicum from the Three Gorges District in Central China:

1. Shrubs or herbs; stems climbing or prostate.......................................................................................................................................2

- Herbs, rarely subshrubs; stems erect, sometimes uppermost parts twining .....................................................................................16

2. Leaf blades mostly lanceolate to linear, less than 2 cm wide; petioles no more than 1 cm long .......................................................3

- Leaf blades ovate, elliptic, or ovate-oblong, more than 2 cm wide; petioles more than 1 cm long.................................................11

3. Stems puberulent along 1 or 2 lines; peduncles less than 1 cm long, or up to 3 cm ( V. pilosellum )..................................................4

- Stems glabrous, or sparsely puberulent but not along lines; peduncles more than 2 cm long ...........................................................6

4. Peduncles up to 3 cm long............................................................................................................................................... V. pilosellum

- Peduncles 5–8 mm long......................................................................................................................................................................5

5. Corollas urceolate, with white tubes and purplish red lobes..................................................................................... V. microcentrum

- Corollas campanulate, yellow ...................................................................................................................................... V. shaanxiense

6. Corollas purplish red ..........................................................................................................................................................................7

- Corollas yellow, yellowish green or white .........................................................................................................................................8

7. Leaf lateral veins obvious, ca. 4 pairs; corollas internally glabrous ................................................................................... V. silvestre

- Leaf lateral veins obscure; corollas internally puberulent...................................................................................................... V. henryi

8. Leaves mostly more than 1 cm wide; coronas less developed, lobes ringlike, inserted near base of gynostegium...........................9

- Leaves mostly less than 1 cm wide; coronas well developed, lobes ovoid, reaching anther base...................................................10

9. Corollas white, lobes much shorter than tubes........................................................................................................... V. hemsleyanum

- Corollas yellowish green, lobes much longer than tubes ............................................................................................ V. pingtaoanum

10. Stems glabrous; leaf blades linear-lanceolate, 5.5–9 cm long; corollas green or yellow........................................................ V. kerrii

- Stems puberulent along 1 line; leaf blades oblong-ovate, 3–5 cm long; corollas purplish red.................................... V. floribundum

11. Stems and leaves densely hirsute or puberulent...............................................................................................................................12

- Stems glabrous or puberulent along 1 line; leaves glabrous or only puberulent on midveins .........................................................13

12. Stems and leaves densely hirsute; corollas dark purplish red; corona lobes horned-falcate, horizontally stellate spreading (former Belostemma ) .................................................................................................................................................................. V. belostemma

- Stems and leaves densely puberulent; corollas purple, or yellow with somewhat purple; corona lobes only slightly swollen, not spreading............................................................................................................................................................................. V. chinense

13. Evergreen woody lianas; leaf blades thinly coriaceous, not cordate at base, no more than 8 × 3 cm ......................... V. pingtaoanum

- Deciduous herbs; leaf blades chartaceous to membranous, usually cordate or shallowly cordate at base, if rounded then mostly larger than 8 × 3 cm ( V. henryanum ) ................................................................................................................................................14

14. Peduncles usually shorter than pedicels; rachis always short, unbranched.................................................................... V. henryanum

- Peduncles usually longer than pedicles; rachis often many branched..............................................................................................15

15. Leaf blades oblong-ovate to hastate, base cordate to rounded; petioles less than 1.5 cm long; corollas purple, 2–3 mm in diameter ...................................................................................................................................................................................... V. floribundum

- Leaf blades ovate or ovate-oblong, base cordate to cuneate or truncate; petioles 1.5 cm or longer; corollas greenish or greenish orange, 4–6 mm in diameter..................................................................................................................................... V. augustinianum

16. Upper stems twining; inflorescences extra-axillary .........................................................................................................................17

- Erect herbs; inflorescences terminal or nearly terminal ...................................................................................................................18

17. Leaves no more than 10 cm long...................................................................................................................................... V. versicolor

- Leaves more than 10 cm long except upper smaller ones .......................................................................................... V. chekiangense

18. Leaf blades ovate, elliptic, or ovate-oblong, less than 3 times as long as wide ...............................................................................19

- Leaf blades linear or narrowly lanceolate, 4 or more times as long as wide....................................................................................21

19. Stems densely tomentose; leaves densely tomentose on both surfaces; inflorescences mostly sessile; corollas dark purplish red .... ............................................................................................................................................................................................. V. atratum

- Stems pubescent along 1 side; leaves puberulent only on veins; inflorescences pedunculate.........................................................20

20. Corollas yellow to brownish or purple, interior puberulent or puberulent except sometimes for lobes ............................. V. forrestii

- Corollas yellow, interior glabrous except sometimes for a few trichomes inside tube ................................................. V. inamoenum

21. Stems puberulent along 1 or 2 lines .................................................................................................................................................22

- Stems glabrous..................................................................................................................................................................................25

22. Stems puberulent along 2 lines..................................................................................................................................... V. glaucescens

- Stems puberulent along 1 line, at least on young branches..............................................................................................................23

23. Leaves 3–6 in a whorl, at least in lower stem; corollas white..................................................................................... V. verticillatum

- Leaves opposite; corollas purplish red or yellow .............................................................................................................................24

24. Leaf blades ovate-lanceolate, 3–10 × 1–3 cm; corollas purplish red ........................................................................... V. mongolicum

- Leaf blades linear-lanceolate, ca. 6 × 0. 5 cm; corollas yellow.................................................................................. V. stenophyllum

25. Leaf blades no more than 5 mm wide; petioles ca. 5 mm long; corollas purpulish red; in wet places ............................ V. stauntonii

- Leaf blades mostly more than 5 mm wide; petioles less than 5 mm long; corollas yellowish green; in dry places .... V. mukdenense