Description from Flora of China
Illigera cucullata Merrill, Univ. Calif. Publ. Bot. 13: 132. 1926.
Lianas. Stem brown, angulate, glabrous. Leaves 3-foliolate; petiole terete, 6-8 cm, striate, glabrous; leaflets: petiolules 0.8-2 cm, glabrous; blade lanceolate-elliptic, elliptic, or ovate, 6-9 × 3.5-6 cm, papery to subleathery, both surfaces glabrous, lateral veins 3- or 4-paired, arising from midvein at ca. 45°, base rounded, apex abruptly shortly acuminate. Cymose panicles axillary, yellow-brown pubescent; bracteoles narrowly elliptic, ca. 2.5 mm, yellow-brown pubescent. Flowers purple-green or green. Outer tepals 6-7 mm, abaxially yellow-brown pubescent. Inner tepals similar to outer ones but shorter, 5-6 mm. Stamens ca. as long as inner tepals; filaments straight in bud; appendages on ca. 1 mm stipe, narrowly ellipsoid, to 3 mm total, membranous, abaxially with open mouth, apex broadly cuneate. Ovary tetragonous, densely yellow-brown pubescent. Interstaminal glands small. Fruit 2-winged; wings suborbicular or ligulate, 4-4.5 cm wide. Fl. Aug-Mar of following year, fr. Jan-Sep.
Illigera trifoliata subsp. trifoliata is characterized by its leaflets, which are 5.5-15 × 3-9 cm, ± pubescent on both surfaces, with lateral veins arising from midvein at 60°-80°; also, its wings of fruit are ligulate, 2.5-4.5 cm wide. It is distributed in India (Andaman Islands), Indonesia, Malaysia, Myanmar, and Thailand.
Valley forests; 1100-1300 m. SE Yunnan [Laos, Thailand, Vietnam].