Platanthera

Abstract, Prasad K. & Rich., Platanthera, 2023, The genus Platanthera (Orchidaceae) in India with two new species, Rheedea 33 (2), pp. 31-52 : 33-34

Key to the species of Platanthera occurring in India

1. Flowers non-resupinate................................... 2

1. Flowers resupinate........................................... 4

2. Flowers whitish-pale pink............. P. superantha

2. Flowers yellow or yellowish-green or green..... 3

3. Racemes secund; flowers deep yellow with dull orange tips...... ............................ P. calceoliformis

3. Racemes non-secund; flowers yellowish-green or green........................................ P. lachungensis

4. Flowers deflexed; spur absent or replaced by small cavity....................................... P. stenochila

4. Flowers not deflexed; spur present.................. 5

5. Spur> 3 cm long................................ P. japonica

5. Spur <2.5 cm long........................................... 6

6. Flowers white or greenish-white; spur amphora-like......................................................................... 7

6. Flowers green or yellowish-green; spur not amphora-like...... ............................................ 10

7. Leaves basal or sub-basal ................. P. uniformis

7. Leaves arranged below the middle or middle of stem................................................................... 8

8. Stem arching; auricles almost as long as anther ........................................................... P. urceolata

8. Stem erect; auricles perfectly shorter than anther................................................................ 9

9. Flowers greenish-white, bell-like......... P. contigua

9. Flowers white with rose tinge or not, not bell-like...... ............................................ P. roseotincta

10.Spur <2 mm long.......................................... 11

10. Spur> 4 mm long.......................................... 13

11. Lip orbicular or orbicular-ovate; spur 0.5–0.7 mm long...... .................................... P. orbicularis

11.Lip oblong-lanceolate or ovate-lanceolate or broadly lanceolate or narrowly deltoid; spur> 1 mm long...... ................................................... 12

12.Viscidium absent....................... P. nematocaulon

12.Viscidium present ............... P. handel-mazzettii 13.Sepals ciliate or dentate along margins......... 14

13.Sepals entire (not ciliate) along margins....... 16

14.Lip distinctly arching; viscidium deeply concave (like a semi-circular tube)...... .... P. dambungensis

14.Lip not arching; viscidium flat...................... 15

15.Leaves undulate at margins; spur strongly S-shaped, directed upwards............. P. bhutanica

15.Leaves entire at margins; spur not S-shaped...... ...................................................... P. pachycaulon

16.Lip basally auriculate; floral bracts diminishing upwards............................................. P. concinna

16.Lip without basal auricles; floral bracts not diminishing upwards..................................... 17

17.Flowers <1 cm across.................................... 18

17.Flowers> 1 cm across.................................... 20

18.Leaf 1; racemes laxly flowered ..... P. leptocaulon

18.Leaves 2 or more; racemes densely flowered... 19

19.Dorsal sepal oblong-lanceolate or ovate-elliptic; viscidium flat.................................... P. bakeriana

19.Dorsal sepal ovate or broadly ovate to sub-orbicular; viscidium concave........ P. dulongensis

20.Floral bracts as long as or slightly longer than flowers, not reflexed ........................ P. stenantha

20.Floral bracts much longer than flowers, spreading and reflexed...... ............ P. sikkimensis

Subgen. Platanthera Sect. Stigmatosae (K.Y.Lang) Efimov, Novosti Sist. Vyssh. Rast. 40: 50. 2009. Platanthera subgen. Stigmatosae K.Y.Lang, Acta Phytotax. Sin. 36(5): 450. 1998. Type: P. exelliana Soó (= P. pachycaulon (Hook.f.) Soó ).