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Oberonia disticha (Lam.) Schltr., Repert. Spec. Nov. Regni Veg. Beih. 33: 132 (1924).
Homotypic Synonyms:
Epidendrum distichum Lam., Encycl. 1: 189 (1783).
Pleurothallis disticha (Lam.) A.Rich., Mém. Soc. Hist. Nat. Paris 4: 49 (1828).
Heterotypic Synonyms:
Cymbidium equitans Thouars, Hist. Orchid.: t. 92 (1822), nom. illeg.
Oberonia brevifolia Lindl., Gen. Sp. Orchid. Pl.: 16 (1830).
Malaxis brevifolia (Lindl.) Rchb.f. in W.G.Walpers, Ann. Bot. Syst. 6: 215 (1861).
Iridorkis equitans Kuntze, Revis. Gen. Pl. 2: 669 (1891).
Oberonia equitans (Kuntze) Schltr., Beih. Bot. Centralbl. 33: 411 (1915), nom. illeg.
Description:
Small to medium size epiphytic plant 3 – 17 cm high, with a single growth or clustered-tufted on a short rhizome, roots whitish, wiry c. 1 mm diam. Pseudobulbs elongate, covered with 2 – 9 caulinary iridiform pairs of leaves. Leaves usually imbricate, bilaterally flattened, triangular-ensiform, acute or acuminate, decreasing towards the apex, more or less fleshy, yellowish green to pale green, 2 – 8.5 × 0.5 – 2.5 cm. Inflorescence sessile or shortly pedunculated, erect, reclining or pendant, 4 – 12 cm long. Peduncle short, about ¼ of the inflorescence. Rachis densely racemose, cylindrical, tapering, verrucose to hirsute, with 10 to more than 100 flowers. Floral bracts lanceolate-acuminate, verrucose to distinctly villose, 1.1 – 2 × 0.8 – 1.1 mm. Flowers very small, not resupinate, c. 2 mm in diam., yellowish green to pale orange, the anther and column paler. Pedicel and ovary cylindrical to fusiform, glabrous to verrucose, 1.3 – 2.3 × 0.4 – 1.5 mm. Dorsal sepal broadly oval to subtriangular, acute, 0.7 – 1.2 × 0.4 – 0.8 mm. Lateral sepals broadly oval 0.6 – 1.2 × 0.4 – 0.7 mm. Petals ovate to linear, apical margin more or less serrate, 0.6 – 0.8 × 0.2 – 0.3 mm. Lip auriculate at the base then flabellate-cordate with the anterior margin bilobed or sinuate to denticulate, deflexed, 0.9 – 1.5 × 0.9 – 1.3 mm. Column short, oblong, roundly bilobed at the apex, 0.4 – 0.5 × 0.2 – 0.3 mm. Anther oval with a small lobule at the anterior margin, c. 0.2 × 0.2 mm. Pollinia ovate c. 1 mm diam. Seed capsule ovoid to globular with distinct rounded ridges, c. 2.5 × 2.5 mm.
Etymology:
Refers to the distichous leaves, Lindley’s Oberonia brevifolia refers to the short leaves.
Recognition:
This is a distinctive small to medium-sized plant with distichous leaves, a long dense inflorescence with numerous very small flowers. Lip auriculate at the base, then flabellate-cordate with the margin bilobed to denticulate.
Oberonia disticha is very variable in plant size and shape, inflorescence and flower shape. Lip morphology, and especially the anterior margin, can vary from deeply dentate to almost entire. If the flowers were much larger it is possible that the various forms would have been classified as distinct species. Oberonia disticha is similar to a number of other Oberonia from Australasia and especially O. equitans (G.Forst.) Mutel (1837: 84) which is very variable itself. The plants are very similar, although O. disticha generally has a narrower basal sheath of the leaf. The rachis of O. equitans is denser, the flowers are about the same size although those of O. equitans are generally smaller. One of the main differences is that the pedicellate ovary of O. equitans is pilose to villose, that of O. disticha glabrous to verrucose (this may not appear so as the villose floral bract often embraces the ovary). The lip of O. equitans is subentire to subquadrate (vs auriculate at the base then flabellate-cordate in O. disticha), the anterior margin of the lip of O. disticha is more deeply and irregularly dentate.
Habitat:
Epiphytic in evergreen forest and high rainfall woodland, usually hanging downwards on trunks and lower branches, 470-1250 m. It tends to be very local in its distribution; in Malawi, for example, it is only found in one small area, although mere are many other places where the habitat is apparently suitable.
Flowering time:
October to August, but mainly June to November in the Comoros; throughout the year but mainly November to March in Madagascar; January to September, but mainly March to April, in Mauritius; March to November, but mainly March to May, in Réunion.
Cultivation:
Intermediate temperatures and moderate shade. This species can be either mounted, if the humidity is kept high, or grown in a pot, where it needs to be watered with cafe as too much moisture will cause the fleshy leaves to rot, although the fine roots do not like to be dried out too much.
Distribution:
Cameroon, Malawi, South Africa (Mpumalanga) , Tanzania, Uganda, Zaire, Zimbabwe. Also in Comoro Islands, Madagascar, Mascarene Islands.
References:
African Orchids Harold Koopowitz, BioScience, Vol. 22, No. 5 (May, 1972), p. 324; African Orchids: X V. S. Summerhayes, Bulletin of Miscellaneous Information (Royal Botanic Gardens, Kew), Vol. 1938, No. 4 (1938), pp. 141-153; Flora Zambesiaca Vol 11 Orchidaceae Part 1 Pope 1995; Field Guide to the Ethiopian Orchids Demissew, Cribb & Rasmussen 2004; Orchids of Madagascar Hermans, Du Puy, Cribb & Bosser 2007; Malaxideae (Orchidaceae) in Madagascar, the Mascarenes, Seychelles and Comoro Islands Kew Bulletin volume 75, Article number: 1 (2020)
Images:
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Photograph© Rogier van Vugt. Image used with kind permission.	Photograph© Rogier van Vugt. Image used with kind permission.	Photograph P. Bernet ©Swiss Orchid Foundation at the Herbarium Jany Renz Image used with kind permission.	Photograph P. Bernet ©Swiss Orchid Foundation at the Herbarium Jany Renz Image used with kind permission.	Photograph P. Bernet ©Swiss Orchid Foundation at the Herbarium Jany Renz Image used with kind permission.