Key to the genus Benthamia A.Rich.
Translated from French to English as best I could
| 1a | Cylindrical spur, having at least 2 mm. 5 long | 2 |
| 1b | Shorter, rounded, scrotiform or bagged spur | 8 |
| 2a | Leaves reduced to sheaths or not yet developed at flowering | 3 |
| 2b | Leaves developed at flowering (sometimes only one, radical) | 4 |
| 3a | Small plant, aphylla; glabrous tubers; bifid spur at the top (massif d’Andringitra, vers 2.300 m) | Benthamia exilis |
| 3b | More robust plant, surrounded at the base with a rosette of leaves (8-10), not developed at flowering; hairy tubers; whole spur (S. de Fianarantsoa, de 1.000 à 1.400 m) |
Benthamia praecox |
| 4a | Clearly three-lobed lip | 5 |
| 4b | Whole lip, sometimes dilated near the base | 6 |
| 5a | A single leaf (radical), narrow; spur hanging, as long as the ovary; unilateral flowers of a sulfur yellow (Ankaratra et Andringitra, de 1.800 à 2.000 m.) |
Benthamia glaberrima |
| 5b | 5-6 stem leaves, wide (up to 75 mm); shorter spur (4 mm) than the ovary; non-unilateral flowers (Mt Ibity, vers 2.000 m.) |
Benthamia bathieana |
| 6a | A single developed leaf; plant 15-30 cm; tubers 2;2 mm spur 5; sepals 3 mm, uninervated; petals with 2 ribs; staminodes 2 times shorter than anther (Andringitra massif, 2.600 m). |
Benthamia monophylla |
| 6b | Two leaves developed; taller plants (45 à 70 cm.) | 7 |
| 7a | Spur 3 mm 5; lip dilated strongly below the middle; anther retusive, more than 1 mm high; very rounded staminodes (Ankaratra, 2.000 m.) |
Benthamia perularioides |
| 7b | 5 mm spur; diamond-shaped lip; shorter apiculate anther (Mt Ibity et Andringitra, 2.000 m.) | Benthamia rostrata |
| 8a | Whole or obscurely toothed or three-lobed lip, but with lateral lobes not reaching half of the median lobe | 9 |
| 8b | Three-lobed lip, lateral lobes at least 2/3 of the middle lobe or only trisinuated, but in this case (B. hermimoides var. angustifolia) with 3 rounded and equal teeth |
20 |
| 9a | Epiphytic plants; leaves generally broad (at most 4 times longer than broad); ear with flowers, unilateral or not; linear and sickle-shaped staminodes, equal to or above the anther; flowers often 5 mm long (without ovary) |
10 |
| 9b | Terrestrial orchid; leaves generally narrow and more than 4 times longer than wide; spike with scattered flowers; broad staminodes, shorter than anther or at most equal; often smaller flowers |
12 |
| 10a | Labelle hollow in obtuse hoof; clearly apiculate anther (Vallée d’Ambolo, E.) | Benthamia catatiana |
| 10b | Labelle concave at the base, but not in the shape of a very hollow and obtuse hoof; anther retusive or obscurely apiculate |
11 |
| 11a | Lower leaf broadly obovate-cuspid, with obtuse cusp; very long staminodes (1 mm. 5), very narrow; laterally toothed lip; median lobe of the whole rostella; spike cylindrical, not unilateral (Mananara, N. E.) |
Benthamia cuspidata |
| 11b | Lower leaf attenuated-acute or sometimes obtuse, but not cuspid-obtuse; shorter staminodes; whole lip; median lobe of the tridenticulate rostella; one-sided flowers |
Benthamia nigrescens |
| Subspecies of Benthamia nigrescens Schltr. | ||
| A1 | More than 3 sheets | B |
| A2 | Up to three sheets | C |
| B1 | Anther shortly apiculate, not surpassed by staminodes; flowers small (3 mm. 1, without ovary); slightly unilateral inflorescence (Réunion) |
subsp. borbonica |
| B2 | Antere retuse, somewhat overwhelmed by staminodes; larger flowers (4 mm. 5, without ovary); infl. markedly unilateral; median lobe of whole rostella (Réunion) |
subsp. secundiflora |
| B3 | Antere retuse, exceeded by staminodes by a third of its length; even larger flowers (5 mm. 5, without ovary); infl. not very clearly unilateral; median lobe of the tridenticulate rostella at the apex (Ankaratra) |
subsp. nigrescens |
| C1 | Staminodes longer than anther retuses; obtuse leaves (E. et Tsaratanana) | subsp. humblotiana |
| C2 | Staminodes shorter than the apiculate anther; acute leaves (Ankaizina) | subsp. decaryana |
| 12a | Entirely whole lip, dug in hoof | 13 |
| 12b | Labell more or less toothed or lobed laterally | 14 |
| 13a | Flowering stem leafy at the base, bearing 2 oval-cuspid leaves; bracts 2 times longer than flowers; oval lip in its outline (Imerina) |
Benthamia misera |
| 13b | Naked flowering stem, the single leaf carried with 2 sheaths by a lateral bud; shorter bracts (Andratamarina, dans le N. E.) |
Benthamia calceolata |
| 14a | Trineve medial sepal; narrow, erect leaves; wide and short staminodes (Andringitra, 2.500 m.)....... | Benthamia macra |
| 14b | Unineral median sepal | 15 |
| 15a | Lower sheaths of deep black; apiculate-acute anther; broad staminodes, shorter than anther (Ikongo, à l’E. d’Ivohibe) |
Benthamia nigrovaginata |
| 15b | Green lower sheaths | 16 |
| 16a | Staminodes much shorter than anther; flowers small (at most 3 mm., without ovary) | 17 |
| 16b | Staminodes equal to anther or longer | 19 |
| 17a | Oval-lanceolate leaves, less than three times longer than wide (Mt Tsaratanana) Benthamia herminioides | subsp. intermedia |
| 17b | Narrow leaves, 7 to 10 times longer than wide | 18 |
| 18a | Compressed spur, longer and almost bidentate at the top (Fort-Dauphin) | Benthamia dauphinensis |
| 18b | Cylindrical spur, shorter, whole (eastern side of the island and Mascareignes | Benthamia africana |
| 19a | Lateral lobes of the labellum subnuls; 2.5-3 mm sepals. long; narrow leaves, 12 mm. wide at most (bassin supérieur du Mangoro) |
Benthamia procera |
| 19b | Lateral lobes of the lip equal to half of the median lobe; 3 mm sepals. 5; leaves up to 35 mm. wide (massif de Manongarivo, 1.200 m |
Benthamia verecunda |
| 20a | Staminodes equal to anther or longer, often linear and curved in false shape | 21 |
| 20b | Broad staminodes, shorter than anther | 23 |
| 21a | Epiphytic plants; wide and short leaves (42 x 14 to 120 x 45 mm.); uninervate sepals; white flowers on one side |
Benthamia nivea |
| Subspecies of Benthamia nivea Schltr. | ||
| A1 | Flowers (without ovary) of 8-10 mm; lip, 5-level (Mt Tsiafajavona, 2.000 m.) | subsp. nivea |
| A2 | Flowers of 5, 5-6 mm; 3-rib lip (Mt Tsaratanana, vers 2.000 m.) | subsp. parviflora |
| 21b | Terrestrial orchid; narrow leaves; uninerve or trinerve median sepal; white or yellowish flowers, unilateral or not |
22 |
| 22a | Trineve medial sepal; flowers yellowish or greenish, small (less than 4 mm.), scattered; 5-6 sheets, measuring up to 160 x 20 mm; linear sickle-cell staminodes (E.?) |
Benthamia elata |
| 22b | Unineral median sepal; flowers twice as large (8-9 mm., without ovary), white, unilateral spike; oblong staminodes, fairly wide (Fort Dauphin) |
Benthamia madagascariensis |
| 23a | Robust plants (stem 6-10 mm. In diameter); broad (20-40 mm.) and thick leaves; dense spike; wide petals, less than twice as long as wide |
24 |
| 23b | Smaller plants; thin and narrow leaves, sometimes nevertheless ovate-lanceolate but then small; loose spike; narrower petals |
25 |
| 24a | Black lower sheaths; uninervate sepals and petals; obtuse anther; palace of the lip without hull | Benthamia humbertii |
| 24b | Green sheaths; trinerval sepals and petals; apiculate anther; palace of the lip decorated with 3 hulls (Réunion) |
Benthamia chlorantha |
| 25a | Unineral median sepal; 2-3 leaves, often ovate-lanceolate (at most 50 x 25 mm.); sparse spike | Benthamia herminioides |
| Subspecies of Benthamia herminioides Schltr. | ||
| A1 | Leaves towards the middle of the stem, lanceolate-linear; lateral lobes of the lip obliterated; obtuse rostolle median lobe (Mt. Tsaratanana) |
subsp. angustifolia |
| A2 | Leaves at the bottom of the stem, ovate-lanceolate | B |
| B1 | Median lobe of the subangulate-acute rostella; rounded side lobes of the lip (Mt. Ibity) | Benthamia herminioides |
| B2 | Median lobe of obtuse rostella; narrow and acute lateral lobes of the lip (Taratanana) | subsp. arcuata |
| B3 | Median lobe of obtuse rostella; rounded side lobes of the lip (Tsaratanana), about 2 times shorter than the median |
subsp. intermedia |
| 25b | Trineve medial sepal; always narrow leaves | 26 |
| 26a | Black base sheaths; median sepal less than 3 mm. long; dense and long cylindrical spike (Mt Tsiafajavona, 2.000 m.) |
Benthamia melanopoda |
| 26b | Green base sheaths; median sepal 4 mm; interrupted spike, fewer flowers (Imerina et Betsileo) | Cynorkis cinnabarina |
