Genoplesium oliganthum D.L.Jones APNI*
Synonyms: Corunastylis oligantha (D.L.Jones) D.L.Jones & M.A.Clem. APNI*
Description: Terrestrial tuberous herb.
Leaf terete, 8–20 cm long by c. 0.15 cm wide, dark green, base reddish, lamina subulate, closely sheathing the scape, 10–18 mm long, 1.5–2.0 mm wide, ending 5–20 mm below the first flower.
Inflorescence 15–30 cm tall, bearing 1–9 flowers in a moderately dense spike 10–20 mm long. Floral bracts closely sheathing, transversely ovate-elliptic, c. 1.5 mm long by 2. mm wide, apiculate. Ovary linear-obovoid, c. 4 mm long, asymmetrically arcuate. Flowers porrect, c. 9 mm wide, brownish to reddish green with prominent red-purple stripes on the dorsal sepal and petals and a red-purple labellum. Dorsal sepal ovate-triangular, c. 5.0–5.5 mm long by 3 mm wide, concave with three prominent purple stripes and purple-tinted margins, margins entire, apex attenuated and acuminate. Lateral sepals linear-lanceolate, slightly falcate, c. 6.5–7 mm long by 1.8 mm wide, not gibbous at the base, widely divergent, margins around the apex inrolled, apex acute or bearing a small apiculus. Petals widely spreading, lanceolate, c. 5.0–5.5 mm long by 1.8 mm wide with three prominent purple stripes and purple margins which are entire, apex acuminate, without a gland. Labellum hinged by a short column foot, porrect, not mobile, lamina elliptic, c. 5 mm long by 2.7 mm wide, fleshy, sharply transversely deflexed in upper third, margins with short to long spreading multicellular filiform cilia 0.3–1.0 mm long, sizes dimorphic, with short and long cilia intermixed along the margin, apex acute; callus extending to immediately below the labellum apex, dark purple-black, thickest and broadest just above the base then drawn out and tapered to an obtuse apex. Column c. 3 mm long by 1.8 mm wide, white or with a red wash, column foot ligulate c. 1 mm long, apex circinate. Column wings shallowly divided by a V-shaped sinus into subequal lobes, upper lobe triangular, white, entire with obtuse or narrowly rounded apex; lower lobe slightly narrower triangular, dark purple, lower margin curved, and ciliate, surface papillose, apex obtuse to subacute. Anther c. 1.3 mm long with a filiform rostrum c. 0.8 mm long. Pollinarium c. 1 mm long; pollinia c. 0.8 mm long, yellow, coarsely granular. Stigma ovate-elliptic c. 1 mm long and 0.6 mm wide.
Flowering: Recorded flowering in February and March.
Distribution and occurrence:
NSW subdivisions: SC, ST, CT
Genoplesium oliganthum can be recognised by 1) the few-flowered inflorescences bearing closely spaced flowers; 2) the prominent purple stripes on the dorsal sepal and petals; 3) the entire margins of the dorsal sepal and petals; 4) the absence of glands on dorsal sepal, petals, and lateral sepals; 5) the acuminate petal apex; 6) the elliptic labellum with 7) a papillose callus extending to rear the labellum apex; 7) the labellum margins bearing a mix of long and short multicellular trichomes; 8) the column wings divided into two equal lobes whose apices are obtuse, and 8) whose lower lobe bears cilia on its margin; and 9) flowers 8-9 mm wide. Genoplesium oliganthum is similar to G. plumosum but G. plumosum has a 'much longer labellum' (Jones 2001: 299). It is also similar to G. rhyoliticum, but G. rhyoliticum has flowers that are around 4 mm wide, not 8-9, and the labellum callus extends into the labellum acuminus, rather than ending beneath it.
Text by Description based on D.L.Jones (2001), with modification by M.A.M.Renner (10 May 2020).
Taxon concept: Jones DL (2001) Six new species and a new combination in Genoplesium R.Br. (Orchidaceae) from eastern Australia. The Orchadian 13(7): 293-307.
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