(Cav. ex Lam.) Urban, Feddes Repert. Beih. 5:123. 1920
O. lagopus Sw.; O. limonensis Rowlee
Balsa, Balso, Lana, Cotton tree
Tree, usually less than 12 m tall but to 30 m where persisting in the older forest, 30-180 cm dbh, sometimes buttressed; wood very lightweight; branchlets, pedicels, lower blade surfaces, petioles, and exposed parts of calyces with a dense layer of brown, stellate, tufted trichomes. Leaves simple, clustered at ends of branchlets; stipules ovate, to 1.5 cm long; petioles thick, 3-40 cm long; blades ovate, acuminate, cordate, 9-40 cm long, 8-35 cm wide, entire to shallowly 3-5-lobed, glabrous above in age, pale below; palmate veins at base 7 (9). Flowers not precocious, leathery, with a pleasant aroma when young; pedicels to 12.5 cm long and 1.5 cm broad; calyx lobes stiffly coriaceous, unequal in shape, to 5.5 cm long, sericeous-villous inside; petals obovate-spatulate, to 15 cm long and 5 cm wide, whitish; staminal column 10-12 cm long, the antheriferous part 5-6 cm long, enlarged at anthesis; pollen with a foul odor, at least in age, evenly distributed over column surface; anthers sessile, longitudinally dehiscent, the theca 1; style completely enveloped by stamens in bud, about as long as stamens at anthesis; stigma stout, spirally 5-sulcate. Capsules long, narrow, to 25 cm long and 2.5 cm diam, black and glabrous outside, densely lanate inside, the valves 5; seeds many, small, ca 5 mm long. Croat 4637, 7214.
Common along the margin of the lake or in disturbed areas, rare in the older forest where it is a large tree. Flowers from August to May, mostly from November to March. The fruits mature from February to August. Leaves fall around June and are replaced in August.
The flowers open at night, sometimes persisting to the following day. At anthesis the anthers, which are somewhat spirally arranged around the style, are unfurled and spread broadly. By the following day they are again closely twisted around the stigma. White-faced monkeys have been seen in the daytime poking their faces into the flower, possibly searching for insects, and their faces become liberally covered with pollen. They probably do not regularly effect pollination because the stigma is then covered, but the flowers may be visited by nocturnal mammals in the same way. Birds often cut holes near the base to obtain nectar. Seeds are principally wind dispersed but probably also water dispersed, made buoyant by the brownish kapok fibers within which they are enveloped.
Native to the New World; pantropical in cultivation. In Panama, known from tropical moist forest in the Canal Zone, Bocas del Toro, Colón, Veraguas, Los Santos, Panama, and Darién, from tropical dry forest in Panama (Taboga Island), from premontane moist forest in the Canal Zone and Panama, from premontane wet forest in Chiriqui, and from tropical wet forest in Veraguas (Atlantic slope).
See Fig. 370.