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Acianthinae_species
Corybas dienemus D.L.Jones
Nomenclature
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Subgenus: CorysanthesSection: Nematoceras
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Synonyms: 2
SUMMARY
Plant: terrestrial tuberous herb, glabrous, deciduous, forming small clonal groups
Tuber: globose to ellipsoid, 1-5 mm long, 1-5 mm wide
Rhizome: (“stolonoid roots”) 5-35 mm long, c. 1 mm thick
Leaf: solitary, held at the substrate surface, cupulate, petiolate; lamina orbicular, 12-20 mm long, 14-23 mm wide, dark green above, silvery green beneath, thick, fleshy; base cordate; apex apiculate, petiole arising below substrate surface, fleshy, 10-20 mm long, 1.5-2 mm thick Peduncle vestigial, green, c. 1 mm long, 1-1.3 mm thick
Bract: erect, membranous, sheathing, ovate-deltate when flattened, 5-6 mm long, 3-3.5 mm wide
Ovary: erect, asymmetric, fleshy, 3-6 mm long, 2-2.5 mm wide
Flower: erect, nestling in the leaf base, green with purplish-red markings, 25-30 mm long, 20-25 mm wide, arising on petiole
Dorsal sepal: incurved with a recurved apex, partially cucullate over the labellum, oblong when flattened, 12-15 mm long, 2.5-3 mm wide, with irregular dark striae; apex acute to acuminate with involute margins
Lateral sepals: exceeding the dorsal sepal, erect, filiform, 30-33 mm long, c. 1.5 mm wide at the base, lightly twisted, with scattered dark marks
Lateral petals: erect to recurved, filiform, 23-25 mm long, c. 1.5 mm wide, with scattered dark marks
Labellum: apex protruding, purplish red; labellum tube 3-5 mm long then abruptly recurved at 90° and expanded into the lamina; lamina ovate, 6.5-7.5 mm long, 12-15 mm wide, the margins incurved, irregular to denticulate; boss not prominent, purplish red; apex shortly caudate
Auricles: not known
Column: procumbent, 3-3.5 mm long, c. 2 mm wide, obscurely winged, anther porrect, c. 1.3 mm long, erostrate, shortly dentiform, pollinia cream to white, sessile on an elliptic viscidium, stigma elliptical, c. 1.2 mm wide, concave, with strongly dentiform margins
Capsule: ovoid, 9-11 mm long, 3-4 mm wide, held erect on a thickened peduncle 4-8 cm long.
Type: ‘N of Bauer Bay, Macquarie Is.’, J.R. Croft 10445, 27 Nov.1989 (CANB!); isotypes (HO!, MEL!, NSW!, WELT!).
Distribution: endemic to Macquarie Island
Ecology: Nematoceras dienemum inhabits the lower coastal terraces (<20m above sea level) and the Green Gorge mire where the vegetation is dominated by bryophytes (mosses) which “float” on a waterlogged underlayer (featherbed).