Trees or shrubs; stipules interpetiolar, linear, adjacent stipules from opposite leaves connate or coherent, the 2 pairs at each node conduplicate and equitant over apical bud, caducous; petiole eglandular; lamina mostly bearing several–many glands in abaxial surface. Inflorescence terminal, mostly unbranched, a raceme of short 2–5-flowered cincinni; bracts and bracteoles persistent, the lowest bracteole and alternate subsequent bracteoles bearing 1 large eccentric abaxial gland; pedicel circinate in bud. Sepals leaving outermost petal exposed in enlarging bud, all biglandular; corolla without a plane of symmetry; petals white or lateral petals white and posterior petal yellow, glabrous or bearing a tuft of hairs abaxially at base of claw; limb of outermost petal conical-galeiform, the other 4 flat or crumpled; posterior petal bearing several marginal glands on proximal half, distally eglandular and entire; lateral petals with margin entire; androecium radially symmetrical; stamens 10, all fertile; filaments very short, densely hirsute on both sides; anthers alike, the locules parallel and tapering distally into 2 sterile awnlike extensions exceeding the slender connective, bearing a tuft of hairs on connective just above insertion of filament; pollen radially symmetrical, 3-colporate; receptacle glabrous on both sides of stamens; gynoecium radially symmetrical; ovary with the 3 carpels completely connate, 1 anterior and 2 posterior, the 3 locules all fertile; styles 3, slender and subulate with the stigmas very small, apical or slightly internal. Fruit dry, indehiscent, a fibrous symmetrical cylindrical or truncate-conoidal nut without a bony endocarp 14–28 mm long, 12–18 mm in diameter, containing only 1 seed. Chromosome number unknown.
Three species of Amazonian Colombia, Venezuela, and Brazil, in lowland forests along rivers or in areas periodically flooded. Like its sister-genus Burdachia, this genus bears fruits adapted for dispersal by water. It is distinguished by its equitant caducous stipules, the galeiform outer petal, and the awnlike extensions of the anther locules. [map]
Photo: G. williamsii