Epipactis, Zinn, 1757

Fateryga, Alexander V., Popovich, Anton V., Fateryga, Valentina V. & Averyanova, Elena A., 2018, New data on the genus Epipactis (Orchidaceae) in the North Caucasus with description of a new species, Phytotaxa 358 (3), pp. 278-288 : 285-286

Key to the species of Epipactis in the North Caucasus

1. Hypochile with two lateral lobes; epichile flexible, ± orbiculate, white; leaves almost glabrous .................................. E. palustris

- Hypochile without lateral lobes; epichile fixed, ± cordate, usually coloured different; leaves with small papillae on edges and nerves ................................................................................................................................................................................................ 2

2. Rachis of inflorescence densely pubescent with well visible hairs .................................................................................................. 3

- Rachis of inflorescence subglabrous or sparsely pubescent with minute hairs visible in a microscope ........................................ 10

3. Ovary strongly pubescent same as rachis of inflorescence; leaves usually ± equal in length to the internodes .............................. 4

- Ovary subglabrous or significantly more sparsely pubescent than the rachis of inflorescence; leaves usually much longer than the internodes ......................................................................................................................................................................................... 6

4. Epichile with one big, irregular, strongly crenate boss near the base, usually dirty-green; sepals shorter than 7 mm; viscidium present ......................................................................................................................................................................... E. microphylla

- Epichile with two separate bosses near the base, greenish-white to bright-pink; sepals longer than 7 mm; viscidium present or absent ................................................................................................................................................................................................ 5

5. Viscidium absent; epichile greenish-white to dirty-pink, ovary 2.5–3.5 mm wide ................................................. E. krymmontana

- Viscidium present; epichile pale-pink to bright-pink, ovary 3.5–4.5 mm wide .................................................... E. condensata s.l.

6. Viscidium indistinct or absent; pedicel usually completely green or with indistinct purplish shade ............................................... 7

- Viscidium well developed at least in young flowers; pedicel strongly purplish at least at the base ................................................ 9

7. Epichile ± equal in length and width, ± flat or with two indistinct small bosses near the base; viscidium always absent; pollinia touching the stigma even in young flowers ...................................................................................................................... E. muelleri

- Epichile longer than wide, with two distinct bosses near the base; viscidium indistinct or absent; pollinia not touching the stigma in young flowers ............................................................................................................................................................................... 8

8. Lateral margins of epichile rolled up; leaves usually yellowish-green ............................................. E. leptochila subsp. leptochila

- Lateral margins of epichile not rolled up; leaves usually pure green ................................................... E. leptochila subsp. neglecta

9. Epichile ± flat or with two indistinct small bosses near the base, usually completely green; sepals shorter than 8 mm; viscidium non-functional, usually present only in young flowers ..................................................................................................... E. pontica

- Epichile with two large bosses near the base, whitish-pink to bright-pink or crimson; sepals longer than 8 mm; viscidium functional, usually present in all flowers, not only in young ones .......................................................................................... E. helleborine s.l.

10. Pedicel much shorter than ovary; epichile ± equal in length and width; viscidium well developed at least in young flowers .......... ............................................................................................................................................................................................ E. persica

- Pedicel ± equal in length to ovary; epichile longer than wide; viscidium indistinct or absent ........................................... E. euxina