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

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