Burmannia, Linnaeus, 1753

Nuraliev, Maxim S., Yudina, Sophia V., Truong, Ba Vuong, Dang, Van Son, Kopylov-Guskov, Yury O., Lyskov, Dmitry F., Kuznetsov, Andrey N., Kuznetsova, Svetlana P. & Zhang, Dianxiang, 2022, A checklist of Burmanniaceae in Eastern Indochina with a new record from Vietnam, Burmannia itoana, Phytotaxa 544 (1), pp. 61-70 : 67-68

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

Partly based on: Gagnepain (1908), Zhang (1999), Wu et al. (2010) and species protologues.

Terminology of flower structure follows Yudina et al. (2022).

1. Plant chlorophyllous (with green leaves and stem)............................................................................................................................2

- Plant apparently achlorophyllous (lacking green coloration in all plant parts)..................................................................................8

2. Plant robust, perennial, with at least some leaves longer than 3 cm and wider than 0.3 cm .............................................. B. disticha

- Plant delicate, annual, with leaves up to 3 cm long and 0.3 cm wide ................................................................................................3

3. Both outer and inner tepal lobes with double margins ...................................................................................................... B. coelestis

- Outer tepal lobes with single or double margins; inner tepal lobes with single margins ...................................................................4

4. Perianth wings narrow, ca. 0.5–0.8 mm wide; outer tepal lobes with single margins.......................................... B. cochinchinensis

- Perianth wings pronounced, at least 1 mm wide (usually 2–3 mm wide); outer tepal lobes with single or double margins.............5

5. Outer tepal lobes with single or double margins (single margins only in China and India); inner tepal lobes ca. 0.4–1.5 mm long (in Eastern Indochina, ca. 1–1.5 mm long) ..................................................................................................................... B. chinensis

- Outer tepal lobes with single margins; inner tepal lobes ca. 0.5–0.8 mm long..................................................................................6

6. Flower 10–13 mm long; outer tepal lobes ca. (1) 1.8–2.2 mm long ............................................................................ B. subcoelestis

- Flower 6–11 mm long; outer tepal lobes ca. 1–1.5 mm long .............................................................................................................7

7. Outer tepal lobes fleshy; inner tepal lobes oblanceolate or spatulate............................................................................... B. luteoalba

- Outer tepal lobes thin; inner tepal lobes lanceolate.............................................................................................................. B. pusilla

8(1). Whole plant bluish..............................................................................................................................................................................9

- Whole plant whitish..........................................................................................................................................................................12

9. Perianth wings prominent, 1–2 mm wide.............................................................................................................................. B. itoana

- Perianth wings narrow (often rib-like), up to 0.8 mm wide .............................................................................................................10

10. Perianth wings rib-like to semi-elliptic, 0.2–0.8 mm wide; outer tepal lobes ca. 1 mm long ........................................... B. wallichii

- Perianth wings rib-like; outer tepal lobes 2.5–4 mm long................................................................................................................11

11. Flower larger (outer tepal lobes 3–4 mm × 1.5–2 mm, inner tepal lobes 2 mm × 1.5 mm, ovary 2.5–3 mm long); outer tepal lobes at apex slightly attenuate and obtuse................................................................................................................................. B. coerulea

- Flower smaller (outer tepal lobes 2.5–3 mm × 1.25–1.5 mm, inner tepal lobes 1 mm × 0.8 mm, ovary 2–2.5 mm long); outer tepal lobes at apex attenuate into long acute caudate tip ca. 1 mm long.............................................................................. B. unguiculata

12(8). Inflorescence dense (usually head-like), with 3–13 flowers; flower wingless or with rib-like perianth wings........... B. championii

- Inflorescence lax (axes usually apparently elongated), with up to 5 (rarely 9) flowers; perianth wings prominent or rarely rib-like ..........................................................................................................................................................................................................13

13. Outer tepal lobes broadly oblong to broadly quadrangular, with emarginate apex; inner tepal lobes absent .................... B. oblonga

- Outer tepal lobes ovate, triangular or oblong, with acuminate, obtuse, rounded or slightly retuse apex; inner tepal lobes absent or present...............................................................................................................................................................................................14

14. Floral tube 1.5–2.5 mm long; outer tepal lobes 0.5–1.2 mm long; inner tepal lobes present ........................................ B. nepalensis

- Floral tube 3.5–5 mm long; outer tepal lobes 1–1.8 mm long; inner tepal lobes absent or present................................. B. lutescens