Gastrodia R.Br.

Martos, Florent, Johnson, Steven D. & Bytebier, Benny, 2015, Gastrodia madagascariensis (Gastrodieae, Orchidaceae): from an historical designation to a description of a new species from Madagascar, Phytotaxa 221 (1), pp. 48-56 : 53

Keys to the species of Gastrodia R.Br. in the tropical Afro-Madagascan region (modified from Cribb et al. 2010)

1. Flowers greenish; sepals free for half their length; dorsal sepal markedly shorter than the lateral sepals; petals spatulate; lip with two rugulose calli at base of midlobe .............................................................................................................................. G. africana

- Flowers brownish to rarely white; sepals free in apical third only; sepals of equal length; petals ovate or broadly ovate; lip lacking two rugulose calli at base of lip midlobe..........................................................................................................................................2.

2. Callus on lip of three ridges, the middle one highest; column foot with two brownish calli at apex .......................... G. rwandensis

- Callus on lip V-shaped, the tip of the V at base of lip midlobe; column foot with two cephaloid tubercular processes at apex.....3.

3. Perianth tube uniformly brown; lip yellow-green with an apricot tip .................................................................................. G. ballii

- Perianth tube not uniformly brown; lip yellow-emerald green or orange-green with an emerald green or whitish tip .................. 4.

4. Perianth tube brownish to blackish brown towards the tips; lip yellow-emerald green with a darker tip; cephaloid tubercular processes emerald green ........................................................................................................................................ G. madagascariensis

4. Perianth tube brownish to translucent white towards the tips or uniformly white; lip orange-green with a whitish-yellowish tip; cephaloid tubercular processes white ................................................................................................................................. G. similis