Tetrapodenia Gleason, Bull. Torrey Bot. Club 53: 289. 1926.—Type: T. glandifera Gleason [=Burdachia sphaerocarpa Adr. Juss.].
Trees or shrubs; stipules intra- and epipetiolar, completely connate, persistent; petiole eglandular; lamina bearing several–many glands in abaxial surface. Inflorescence terminal, single or 2 or 3 together, each usually divided near base into 3 (–5) axes, each axis a raceme of short 1–6-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 bilaterally symmetrical, the posterior petal strongly differentiated from the lateral 4, with a thick erect claw and large marginal glands at least on proximal half of limb and often continuing over the apex; petals pink or white, glabrous; limb of outermost petal concave; lateral petals with the margin entire; androecium radially symmetrical, glabrous; stamens 10, all fertile; filaments opposite sepals slightly longer than those opposite petals, connate at base; anthers all ± alike or some larger than others, the locules parallel and rounded at apex and often exceeded by the thick, fleshy connective; pollen radially symmetrical, 3-colporate; receptacle glabrous on both sides of stamens; gynoecium at least apparently radially symmetrical; ovary with the 3 carpels completely connate, 1 ± anterior and 2 ± posterior, 3-locular but 1 of the posterior locules empty and smaller; styles 3, slender and subulate with the stigmas very small, slightly internal and decurrent. Fruit dry, indehiscent, a fibrous or aerenchymatous nut without a bony endocarp, 9–28 mm long, 8–19 mm in diameter, symmetrically spheroidal or conoidal, containing only 1 seed. Chromosome number unknown.
Two or three species in lowland forests near rivers or in low, periodically flooded places, in Guyana and Amazonian Venezuela, Colombia, Brazil, and Peru. The dry indehiscent fruits are well adapted for dispersal by water. [map]
Burdachia is closely related to another genus of Amazonian trees bearing fibrous or aerenchymatous fruits, Glandonia, but it is readily distinguished by its persistent intrapetiolarly connate stipules, glabrous filaments, and anthers with rounded locules and thick, fleshy, apically enlarged connectives. In flower Burdachia can be confused with Byrsonima, but that genus never has glands on the leaves or bracteoles.
Etymology: This genus was named for Karl Friedrich Burdach (1776–1847), professor of medicine at Leipzig, Dorpat, and Königsberg (Wittstein, 1856).