Key to the species of Nervilia occurring in Africa
All characters used refer to unpollinated flowers in full anthesis (A) and to fully developed and mature leaves (B). Variable species are keyed out in more than one place. The variability of some of the species makes it necessary, in extreme cases, to know both flowering scape and leaf for a certain determination. However, most "single-aspect" specimens (leaf only or flowers only) are easily determinable.
Unfortunately, "geographical characters" have had to be used to separate the leaves of N. pectinata and N. subintegra. Apart from a difference in mean size they are indistinguishable.
Key to flowering specimens of the genus Nervilia

1 Lip with spur 2
  Lip without spur 3
2 Lip white with purple markings; scent of camphor, spur 1.5-3 mm Nervilia pectinata
  Lip mainly lilac, purple or red; scent sweet; spur 3-4.2 mm Nervilia stolziana
3 Flower single 4
  Flowers 2-several 16
4 Lip mainly white, without strong markings, often with yellow central line 5
  Lip with distinct red or purple markings 8
5 Lip ± horizontal, not trumpet-shaped, very obscurely trilobed with entire margin Nervilia subintegra
  Lip erect, trumpet-shaped, distinctly trilobed or with fringed margin 6
6 Lip above covered by short, inflated, club-shaped hairs, flower large, sepals 25-40 mm long, Madagascar only Nervilia leguminosarum
  Lip with much longer, often hairlike outgrowths (seldom glabrous), flower smaller, sepals < 20 mm long 7
7 Lip with a tuft of spaghetti-like outgrowths, flower very small, sepals mostly less than 13 mm long Nervilia petraea
  Lip with thin, hairlike outgrowths (sometimes lacking) and 3 rows of blunt tubercles or elongated, tapering emergences, flower larger, sepals mostly more than 13 mm long Nervilia crociformis
8 Lip side lobes with strong reddish (or greenish) venation, midlobe recurved 9
  Lip side lobes without strong venation, midlobe seldom recurved 11
9 Column 9-13.5 mm, inflorescence normally 1-flowered, sepals reddish Nervilia ballii
  Column 10-25 mm, inflorescence normally several-flowered, sepals reddish or green 10
10 Column 10-15 mm, inflorescence normally 2-12-flowered, sepals green Nervilia bicarinata
  Column 16-25 mm, inflorescence normally 2-3-flowered, sepals reddish Nervilia shirensis
11 Flower cleistogamous Nervilia lilacea
  Flower not cleistogamous 12
12 Lip sidelobes acute, lip glabrous, Madagascar only Nervilia lilacea
  Lip sidelobes rounded, lip glabrous or hairy 13
13 Lip densely or sparsely pubescent, hairs long, Madagascar only Nervilia affinis
  Lip glabrous, sometimes with short papillae on coloured parts, African mainland 14
14 Lip midlobe with erect or rolled-in edges Nervilia adolphi
  Lip midlobe almost flat with convex central ridge 15
15 Lip midlobe (epichile) much longer and wider than hypochile Nervilia fuerstenbergiana
  Lip midlobe (epichile) of approximately the same length and width as hypochile Nervilia lilacea
16 Inflorescence 4-12-flowered 17
  Inflorescence usually 2-3-flowered, ± secund 19
17 Flowers yellow with red veining; column 15-19 mm (lowest flower) Nervilia renschiana
  Flowers yellow-green with purple or green veins; column 7-15 mm 18
18 Column 10-15 mm Nervilia bicarinata
  Column 7-11 mm Nervilia kotschyi
19 Flowers small, column 7-11 mm; sepals < 26 mm Nervilia kotschyi
  Flowers large, column 16-25 mm; sepals > 25 mm Nervilia shirensis

World Checklist of Monocotyledons. The Board of Trustees of the Royal Botanic Gardens, Kew. Published on the Internet; accessed 06/11/2013

Nervilia subintegra Summerh., Bull. Misc. Inform. Kew 1938: 150 (1938).
Heterotypic Synonyms:
Nervilia toillieziae N.Hallé, Adansonia, n.s., 11: 455 (1971).
Erect, terrestrial herb, 5—13 cm tall, glabrous except for leaf and subterranean parts. Tuber subspherical or ovoid, 4-15 by 9-17 mm. Leaf solitary, appearing after flowering, horizontal but not prostrate, above sparsely covered with short hairs; blade star-shaped, (7—)9(—1 l)-lobed, (2.5-)4-9(-13) cm broad; veins (7—)9(—11); petiole (2-)3-9 cm long, sulcate with 1 or 2 sheathing cataphylls. Scape erect, terete, 1-flowered, with (2 or) 3 sheathing cataphylls, lengthening to 17-27 cm when fruiting. Flower small, more or less horizontal, 25-40 mm diam. Bract 1 (occasionally 2), linear, 7-15 by 0.7 mm. Sepals and petals spreading, subequal, ligulate, acute, greenish brown with reddish veins; lateral sepals 12-22 by 2-5 mm; petals slightly shorter than sepals. Lip 10-17 by 5—7 mm, very obscurely 3-lobed, mainly pink with yellow midline in proximal half, tightly clasping column; apical part with convex central ridge; sidelobes with radially running furrows and ridges. Gynostemium clavate, glabrous, pale yellow (6-)7-10 mm. Anther pale yellow, c. 2 mm, pollinia yellow. Capsule 14 mm.
Dense and humid lowland and submontane forest, forest edge, gallery forest, occasionally secondary forest and tree savanna; 300-1100 m.
W. Trop. Africa to Sudan

Nervilia shirensis (Rolfe) Schltr., Bot. Jahrb. Syst. 45: 403 (1911).
Homotypic Synonyms:
Pogonia shirensis Rolfe in D.Oliver & auct. suc. (eds.), Fl. Trop. Afr. 7: 187 (1897).
Heterotypic Synonyms:
Pogonia buchananii Rolfe in D.Oliver & auct. suc. (eds.), Fl. Trop. Afr. 7: 187 (1897).
Nervilia buchananii (Rolfe) Schltr., Bot. Jahrb. Syst. 45: 403 (1911).
Erect terrestrial herb (10)15–44 cm tall, glabrous except for lip and subterranean parts. Tuber 1.5–3 × 1.5–2.8 × 0.8–2 cm, subspherical or ovoid, 4–7-noded.Leaf solitary, appearing after flowering, erect to suberect, large, 6–16 cm long and 3.5–11 cm wide, ovate to almost round, glabrous, pleated; apex obtuse to acute or slightly acuminate; base attenuate to truncate or slightly cordate; veins 6–10; petiole 5.5–17 cm long, sulcate with 1–5 sheathing cataphylls when young. Scape erect, terete, (1)2–3-flowered, with 2–4 sheathing cataphylls. Flowers large, more or less secund; bracts 22–31 mm long, linear, setose, acute. Sepals and petals subequal, linear-lanceolate, acute, greenish-yellow with red veins and a general reddish tinge to the outside; lateral sepals slightly oblique, 25–42(45) × 5.2–7.5 mm; petals slightly shorter than sepals. Lip cream or pale yellow with prominent red or purple venation, (19)24–40 × 22–31 mm, ovate, 3-lobed, bearing 2 parallel fleshy pubescent ridges running from base of lip to base of mid-lobe; side lobes oblong, rounded to obtuse, erect, enclosing the column; mid-lobe ovate, obtuse, reflexed. Column curved, 16–25 mm long, clavate, glabrous; anther front rim with 2 protruding teeth; pollinia yellow, 3.9–5.2 mm; stigmatic surface 5–8 mm in diameter. Capsule 14–19 × 12 mm.
Brachystegia woodland, riverine forest, grassland, and in pine, cypress or Gmelina plantations 480–1950 m.
Chad to S. Trop. Africa
Orchid Monographs 5 (1991); La Croix, I. & Cribb, P.J. (1995). Orchidaceae (Part 1) Flora Zambesiaca 11(1); La Croix, I. et al. (1991). Orchids of Malawi A.A. Balkema, Rotterdam; Cribb, P.J. (1984). Orchidaceae (Part 2) Flora of Tropical East Africa
Click on each image to see a larger version.

Habitat/In situ
Nervilia shirensis (Rolfe) Schltr. 01
Photograph© Biodiversity
and Landscape Unit.
Image used with kind

Nervilia renschiana (Rchb.f.) Schltr., Bot. Jahrb. Syst. 45: 404 (1911).
Homotypic Synonyms:

Pogonia renschiana Rchb.f., Otia Bot. Hamburg.: 73 (1881).
Heterotypic Synonyms:
Nervilia insolata Jum. & H.Perrier, Ann. Fac. Sci. Marseille 31: 192 (1912).
Nervilia grandiflora Schltr., Ann. Transvaal Mus. 10: 241 (1924), nom. illeg.
Nervilia natalensis Schelpe, Orchid Rev. 74: 394 (1966).

This species is very closely related to N. renschiana. Differing in that its petiole is nearly absent leaf, closely set to the soil, at least twice as large (8-24 cm in diameter), orbicular, cordate basally and acuminate acute apically; labellum tipped with a triangular-acute acumin, margins gradually attenuate, not dilate lobed laterally-obtuse; column longer (2-2.2 cm); the 2 crests on the bane of the labellum thinner, separated by a depressed interval, densely villous, taller than the interval, in the lower half the hairs are taller; the anther similar (with tetrads arranged in a linear row, pollina 2 per lobe, without viscidiums, the same size) but provided in front and apically with 2 small points. The anther 4 mm long and 2 mm wide and the rostellum in the form of a strap, 1.5 mm wide and l mm tall.

On limestone rocks, bare, not near the sea; flowering in November-December

Tanzania to S. Africa, Madagascar

Nervilia petraea (Afzel. ex Sw.) Summerh., Bot. Mus. Leafl. 11: 249 (1945).
Homotypic Synonyms:
Arethusa petraea Afzel. ex Sw., Neues J. Bot. 1: 62 (1805).
Nervilia afzelii Schltr., Bot. Jahrb. Syst. 45: 402 (1911), nom. superfl.
Heterotypic Synonyms:
Aplostellis simplex Thouars, Hist. Orchid.: t. 24 (1822).
Arethusa simplex Thouars, Hist. Orchid.: t. 24 (1822).
Stellorkis aplostellis Thouars, Hist. Orchid.: t. 24 (1822), nom. illeg.
Epidendrum simplex (Thouars) Spreng., Syst. Veg. 3: 736 (1826).
Aplostellis ambigua A.Rich., Mém. Soc. Hist. Nat. Paris 4: 36 (1828).
Aplostellis truncata Lindl., Gen. Sp. Orchid. Pl.: 411 (1840).
Pogonia thouarsii Blume, Coll. Orchid.: 152 (1859).
Pogonia simplex (Thouars) Rchb.f., Xenia Orchid. 2: 92 (1865).
Nervilia simplex (Thouars) Schltr., Bot. Jahrb. Syst. 45: 401 (1911).
Nervilia afzelii var. grandiflora Summerh., Bull. Misc. Inform. Kew 1936: 222 (1936).
Erect terrestrial herb 2-8.5(-10.5) cm tall, glabrous except for lip and subterranean parts. Tuber subspherical or ovoid, 3-8 mm diam., (2-)3(-4)-noded. Leaf solitary, appearing after flowering, prostrate, cordate to almost orbicular, sometimes obscurely angled, glabrous, dark olive green above, often with silvery rays, purple below, 6-15 by 8-25 mm; veins 7-9(-10); petiole 0-1 cm long, sulcate with 1-2 sheathing cataphylls. Scape erect, terete, l-flowered, with (1-)2-4 sheathing cataphylls, lengthening to c. 10 cm when fruiting; bract 0-1.5 mm. Flower more or less erect. Sepals and petals spreading, closing again after about 8 hours anthesis or earlier if pollinated, subequal, linear-ligulate, acute, brownish green, lateral sepals oblique, 8-15.5 by 3.5 mm. Lip obovate-cuneate, to 9-15.5 by 8 mm, 3-lobed, white with a yellow centre; laterallobes oblong-triangular, obtuse; midlobe fimbriate, suborbicular, with numerous subulate appendages. Gynostemium clavate, glabrous, 4-9 mm; anther white or purple; pollinia pale yellow or purple, c. 1.5 mm; ovary c. 3 mm; capsule c. 9 mm.
On bare rocks or in dry prairies from 0-1000 m alt.; very rare, flowering in December-January.

Trop. Africa, W. Indian Ocean

Click on each image to see a larger version.

Botanical Drawing / Herbarium
Photograph copyright Swiss Orchid Foundation at the Herbarium Jany Renz Image used with kind permission.