(L. C. Rich.) DC., Prodr. 9:185. 1845
A. pachycalyx Sprague
Liana; outer bark brown, flaky; branches terete with prominent lenticels even on youngest branchlets, the nodes with interpetiolar glandular fields; tendrils simple; pseudostipules lacking. Leaves 2- or 3-foliolate, bicolorous, often drying reddish above; petioles l.6-6.1 cm long; petiolules 0.8-3.3 cm long; leaflets oblong-ovate to broadly ovate, sharply to bluntly acuminate, cuneate to cordate at base, 4.5-17 cm long, 2.5-11 cm wide, minutely pubescent or glabrous above, densely white-tomentulose below, usually with a few sunken glands in basal axils. Inflorescences terminal, showy, pyramidal thyrses; buds lavender; flowers magenta, drying rusty brown; calyx cupular, truncate, 4-6 mm long; corolla 2-3.5 cm long, 2-3 cm broad, densely pubescent outside and on lobes inside, sometimes extending onto 2-lobed side of corolla, the tube white inside; stamens inserted 5-6 mm from base of corolla; filaments retrorse-barbate at point of fusion with tube, the longer pair 1.5-1.6 cm long, the shorter pair 1.1-1.4 cm long, the thecae divaricate, 2-2.5 mm long, shedding pollen in bud; staminodium 4-6 mm long; pistil 1.7-1.8 cm long; ovary linear-oblong, 2-2.5 mm long, finely lepidote; style open and apparently receptive in bud; stigmas recurved, held at level of longest stamens. Capsules 13-34 cm long, ca 1.2 cm wide, acuminate at apex, acute at base, somewhat warty and glandular-lepidote, with a weak medial ridge; seeds to 1 cm long and 3 cm wide. Croat 5228, 11099.
Common over the canopy of the forest, extending down to near the lake. Flowers abundantly from November to February (one shore plant in July); individuals flower for about 1 month, with many flowers open at a time. The fruits mature mostly from February to April.
Recognized by its small flowers and densely white-tomentose lower leaf surface.
Southern Mexico to Colombia and Amazonian Brazil. In Panama, commonly known from tropical moist forest in the Canal Zone, Veraguas, Herrera, Panama, and Darién; sporadically from tropical dry forest in Herrera and Coclé, from premontane moist forest in the Canal Zone, Coclé, and Panama, from premontane wet forest in Chiriqui, and from tropical wet forest in Colón.