Platanthera Richard (Richard 1817

Key to Platanthera species of the Pan-Himalaya 1a. Flowers less than 1 cm across; spur, if present shorter than 4 mm. 2a. Spur absent; leaves shorter than 2.5 cm. 3a. Leaf single, ovate.............................................................................................................................................................. P. milinensis 3b. Leaves 2–3, lanceolate to linear 4a. Leaves alternate; lip entire .............................................................................................................................................. P. stenochila 4b. Leaves subopposite; lip 3-lobed .................................................................................................................................... P. xizangensis 2b. Spur present; leaves longer than 2.5 cm. 5a. Lip deeply concave; tuberoids stoloniferous............................................................................................................. P. calceoliformis 5b. Lip more or less flat; tuberoids not stoloniferous. 6a. Flowers usually fully opened; spur usually not clavate.................................................................................................. P. minutiflora 6b. Flowers not fully opened; spur strongly clavate, often saccate 7a. Tepals shorter than 2 mm; flowers adjacent to inflorescence axis. 8a. Spur 1.0– 1.5 mm long; viscidium reduced................................................................................................................ P. nematocaulon 8b. Spur 1.5–2.0 mm long; viscidium narrowly ovate ................................................................................................ P. handel-mazzettii 7b. Tepals longer than 2 mm; flowers not strongly adjacent to inflorescence axis. 9a. Inflorescence secund 10a. Stem arching; leaf blade lanceolate................................................................................................................................... P. urceolata 10b. Stem erect; leaf blade broadly ovate to ovate....................................................................................................................... P. anatina 9b. Inflorescence symmetrical or subsecund 11a. Flowers overlapping with each other 12a. Flowers white to yellow, not bell-like ............................................................................................................................ P. roseotincta 12b. Flowers greenish-white, bell-like (not fully opening) 13a. Petals not reflexed; lip yellowish-green ............................................................................................................................. P. contigua 13b. Petals highly reflexed; lip white ................................................................................................................................ P. deergongensis 11b. Flowers not overlapping with each other, distinctly spirally arranged or alternate 14a. Leaves 2, subopposite; spur cylindric .............................................................................................................................. P. gonggana 14b. leaf 1(2); spur saccate 15a. Leaf blades sub-orbicular; flowers greenish-white ......................................................................................................... P. linzhiensis 15b. Leaf blades broadly ovate to lanceolate or elliptic to oblong; flowers white 16a. Tepals lanceolate; lip broadly lanceolate.......................................................................................................................... P. uniformis 16b. Tepals ovate to oblong-elliptic; lip oblong-ligulate........................................................................................................ P. superantha 1b. Flowers over 1 cm across; spur longer than 5 mm 17a. Leaves subopposite; spur horizontal or directed upwards 18a. Plants 20–60 cm tall; flowers usually white........................................................................................................................... P. densa 18b. Plants up to 15 cm tall; flowers yellowish green or green .......................................................................................... P. lachungensis 17b. All leaves distinctly alternate; spur pendulous 19a. Sepals papillose at margins; lateral stigma lobes protruding forward 20a. Petals distinctly spreading; plant up to 32 cm tall............................................................................................................. P. concinna 20b. Petals connivent into a hood; plant height variable 21a. Spur more than 10 mm long 22a. Inflorescence laxly 2–10-flowered, secund................................................................................................................... P. leptocaulon 22b. Inflorescence subdensely 10–35-flowered, symmetrical 23a. Spur equal or slightly longer than ovary ....................................................................................................................... P. medogensis 23b. Spur usually twice the length of ovary............................................................................................................................. P. bakeriana 21b. Spur less than 9 mm long 24a. Spur distally dilated; viscidium flat............................................................................................................................. P. pachycaulon 24b. Spur distally not dilated; viscidium concave 25a. Rachis not dentate; floral bracts up to 30 mm long, margin ciliate.............................................................................. P. yadongensis 25b. Rachis dentate; floral bracts up to 20 mm long, margin dentate ............................................................................... P. dambungensis 19b. Sepals not papillose at margins; lateral stigma lobes not protruding forward 26a. Tuberoids stoloniferous; stigma convex or flat 27a. Lip longer than 10 cm; lateral walls of column projecting forward 28a. Tepals 6–10 mm long; lip with a callus at base.................................................................................................................. P. japonica 28b. Tepals 4–7 mm long; lip without callus at base.................................................................................................................. P. finetiana 27b. Lip shorter than 10 cm; lateral walls of column not projecting forward 29a. Spur 4–6 mm long; lip oblanceolate............................................................................................................................... P. ussuriensis 29b. Spur 7–12 mm long; lip blade suborbicular .................................................................................................................... P. fuscescens 26b. Tuberoids not stoloniferous; stigma generally concave 30a. Lateral petals with strongly papillose margins; spur clavate............................................................................................ P. oreophila 30b. Lateral petals with smooth margins; spur variously shaped 31a. Lip suborbicular, base constricted into claw ................................................................................................................... P. ovatilabris 31b. Lip ligulate, base wide 32a. Spur less than 10 mm long; lip less than 4 mm long..................................................................................................... P. dulongensis 32b. Spur more than 10 mm long; lip more than 5 mm long 33a. Petals connivent with median sepal into a hood..................................................................................................................... P. minor 33b. Petals not connivent with median sepal into a hood 34a. Lip three lobed at base; viscidium orange...................................................................................................................... P. sikkimensis 34b. Lip usually entire at base; viscidium green 35a. Inflorescence 4–12-flowered; median sepal broadly ovate .............................................................................................. P. bhutanica 35b. Inflorescence 7–25(35)-flowered; median sepal narrowly ovate ..................................................................................... P. stenantha