Tendriled liana; trunk to 7 cm diam, involuted, twisted, warty, lacking milky sap (at least sometimes); stems with milky sap, glabrous to villous especially when young, (3) 5-ribbed (the ribs on larger stems in turn 2-ribbed), often sparsely armed with short prickles, especially larger stems; tendrils bifid, axillary. Leaves biternate to bipinnate or tripinnate, 10-40 cm long, often much reduced on inflorescence; stipules linear, paired, ca 1 cm long (on juveniles); petioles with marginal ribs above; rachis winged; leaflets 9-26, ovate to elliptic, acute to bluntly acuminate, rounded to attenuate at base, 2-8 cm long, 1.5-5 cm wide, ± glabrous to sparsely pubescent especially on veins, the margins sinuate-dentate near apex (conspicuously dentate on juveniles). Thyrses in solitary and axillary racemes or on tendrils or in terminal or axillary racemose panicles; flowers white, sweetly aromatic, ca 4 mm long; pedicel and calyx densely pubescent; sepals elliptic, ca 2.5 mm long, reflexed or spreading at anthesis; petals spatulate to obovate, 2.3-3.5 mm long, the glands large, ovoid, orange, glabrous, subtending petals, the scales of the anterior petals orbicular, nearly three-fourths as long as petals, their appendages slender, attached laterally to appendage of neighboring scale by villous pubescence, pendent nearly to base of scale, the crest yellow, hammer-shaped, the lateral petals borne on large glands; stamens 8; filaments flattened, sparsely villous; ovary 3-sided, glabrous. Fruits ovate-cordate, 1.7-2.7 cm long, glabrous, the cells with raised veins, the wing sometimes not constricted above seed. Croat13959, 14611.
Common both as an adult plant and as a seedling in the forest. Flowers from February to April (sometimes from January). The fruits mature from March to May.
This is vegetatively the most variable species of Serjania on the island.
Mexico to Colombia and Venezuela. In Panama, known from tropical moist forest in the Canal Zone, Bocas del Toro, Chiriqui, Veraguas, Los Santos, Herrera, Panamd, and Darien, from premontane wet forest in Chiriqui (Boquete) and Veraguas, and from tropical wet forest in Coclé and Panama.