| Flower solitary. Upper sepal narrow, concave; lateral and petals lanceolate. Lip 3-lobed; disc with raised glands. Column long, winged above; wing produced upwards into 2 toothed lobes | 18. Adenochilus. |
| Flowers 1 or 2. Upper sepal broad, concave; lateral lanceolate. Petals minute. Lip broad, undivided; disc smooth. Column long, equally winged, wings not produced upwards | 19. Townsonia. |
| Flowers several. Sepals and petals narrow, acuminate. Lip spreading, broad, concave. Column long | 12. Acianthus. |
| Flowers 2–3. Sepals and petals linear, obtuse. Lip spreading, narrow, flat. Column long, winged above | 13. Cyrtostylis. |
| **** Leafless. Stem tall, with brown sheathing scales. | |
| Sepals and petals united into a 5-lobed ventricose tube | 21. Gastrodia. |
The above clavis is purely artificial, and is solely intended to facilitate the determination of the genera. The following arrangement, which is adapted from Hooker and Bentham's "Genera Plantarum" and Engler's "Pflanzenfamilien," is more natural and shows the sequence adopted in this work:—
Tribe I. Epidendreæ.—Anther lid-like, usually deciduous; cells parallel, distinct. Pollinia waxy, 1–4 in each cell, free, or those of each cell connected by a viscid appendage, not attached by their bases or by a caudicle to the rostellum.
1. Dendrobium. 2. Bulbophyllum. 3. Earina.
Tribe II. Vandeæ.—Anther lid-like, usually deciduous, resting on the rostellum; cells usually confluent. Pollinia waxy, usually 2 or 4 in superposed pairs, attached singly or in pairs to a gland or process of the rostellum, which comes away with them when they are removed.
4. Sarcochilus.
Tribe III. Neottieæ.—Anther lid-like or erect and persistent; cells distinct, parallel. Pollinia granular or powdery.
Subtribe 1. Spirantheæ.
5. Spiranthes.
Subtribe 2. Thelymitreæ.
6. Thelymitra.
Subtribe 3. Diurideæ.
7. Orthoceras. 8. Microtis. 9. Prasophyllum.
Subtribe 4. Pterostylideæ.
10. Caleana. 11. Pterostylis.
Subtribe 5. Caladeniæ.
12. Acianthus. 13. Cyrtostylis. 14. Calochilus. 15. Lyperanthus. 16. Caladenia. 17. Chiloglottis. 18. Adenochilus. 19. Townsonia.
Subtribe 6. Pogonieæ.
20. Corysanthes.
Subtribe 7. Gastrodieæ.
21. Gastrodia.
