Rhizome terete, 10--15 cm. Stem twining or erect, 0.3--2.5 m tall, sparsely retrorse pubescent or becoming glabrous. Basal leaf 1, and proximal cauline leaves long petiolate, distal ones shortly petiolate, smaller above; petiole 3--35 cm; leaf blade pentagonal-reniform, 6.5--9.5(--18) × 9.5--17(--25) cm, both surfaces sparsely appressed pubescent; base cordate, 3-parted beyond ± middle; central lobe rhombic-obtrapezoid, broadly rhombic or rhombic, 3-lobed, margin dentate above middle; lateral lobes obliquely flabellate, unequally 2-fid. Inflorescence 6--14 cm, 3--8-flowered; rachis and pedicels densely spreading pubescent; bracts linear, 3--3.5 mm. Pedicels 5--9 mm, with 2 bracteoles at base or middle; bracteoles similar to bracts. Sepals purplish or ± white, abaxially spreading pubescent; lower sepals 0.8--1.2 cm; lateral sepals 1--1.5 cm; upper sepal cylindric, 1.3--2 cm high, middle 2.8--5 mm in diam., shortly beaked, lower margin 1.3--2 cm. Petals glabrous; lip linear, conspicuous; spur circinate, longer than lip. Stamens glabrous; filaments entire. Carpels 3; ovary sparsely spreading pubescent or glabrous. Follicles erect, ca. 1.2 cm. Seeds ca. 2.5 mm. Fl. Aug--Sep. 2n = 16*.
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