Macroptilium atropurpureum. Photo copyright ©2007 by Kristopher Kupsch
Morphological description. Perennial herb with deep, swollen taproot and trailing, climbing and twining stems. Stems at the base of older plants fibrous, >5 mm diameter; younger stems mostly 1-2 mm diameter, pubescent to densely pilose with white hairs; occasionally forming nodal roots under ideal conditions. Leaves trifoliolate; leaflet blades 2-7 x 1.5-5 cm, darker green and finely hairy on the upper surface, grey-green, pubescent on the lower surface, with leaf margins sparsely to densely, finely ciliate. Lateral leaflets ovate to narrowly elliptical, obtuse, mostly with one or two, shallow to deep lobes on the outer margin; terminal leaflet rhomboid, with or without single lobe either side. Inflorescence a raceme comprising 6-12 often paired flowers on a short rachis, peduncle 10-30 cm long. Flower: calyx campanulate-tubular, hairy, tube 8-9 mm long and 3 mm wide, corolla with conspicuous wings 15-17 mm long, deep purple with reddish tinge near base; standard smaller than wings, obovate deltoid at base, reflexed, yellow-green with a purple tint; keel pink, forms a complete spiral. Pods straight, linear-cylindrical, acuminate-beaked, pubescent, 5-10 cm long, 3-5 mm diameter, containing up to 12 (-15) seeds. Pods dehisce violently (shatter) when ripe. Seeds speckled, light brown to black, flattened ovoid , 4 x 2.5 x 2 mm, 75,000/kg.
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