Orchidantha

KEY TO THE BORNEAN SPECIES OF ORCHIDANTHA View in CoL

1. Lateral sepals overlapping and supporting the labellum. 2

1. Lateral sepals spreading, not supporting the labellum... 7

2. Leaves of adult plants clearly petiolate.............. 3

2. Leaves of adult plants without petiole, base attenuate.. 6

3. Labellum broadly elliptic, shallowly boat-shaped, dark purple at base, gradually changing to warm yellow towards apex................................... O. quadricolor View in CoL

3. Labellum more or less involute with prominently raised midrib and more or less undulate margins, plain dark purple... 4

4. Flowers small: sepals and labellum not exceeding 2.5 cm.................................... O. micrantha View in CoL

4. Flowers large: sepals more than 9–16 cm long and labellum 7–14 cm long.................................. 5

5. Sepals c. 9 cm long. Labellum c. 7 cm long.. O. holttumii View in CoL

5. Sepals 14–16 cm long. Labellum 12.5–13.5 cm long...................................... O. megalantha View in CoL

6. Sepals 73–100 × 11–12 mm. Petals whitish with purple tips................................ O. sabahensis View in CoL

6. Sepals 57–70 × 11–14(–18) mm. Petals plain dark purple....................................... O. suratii View in CoL

7. Labellum purple with yellow or whitish apex, sometimes also with whitish midrib ( Sarawak)..................... 8

7. Labellum blackish violet or dark purple throughout..... 9

8. Lamina 70–120 × 11–15 cm. Labellum purple with whitish apex................................... O. inouei View in CoL

8. Lamina 22–40 × 6–10 cm. Labellum purple with yellow apex............................. O. ranchanensis View in CoL

9. Robust plant to 1.5 m tall. Labellum 97–117 × 40–45 mm, including to 7 mm long acumen.......... O. grandiflora View in CoL

9. Small plant c. 0.3 m tall. Labellum c. 21 × 3.5 mm......................................... O. borneensis View in CoL