Gaertnera Schreb., Gen. Pl. ed. 8: 290. 1789, nom. rej., non Gaertnera Lam., nom. cons.—Schreber published no species or combinations in Gaertnera.
Molina Cav., Diss. 9: 435. Jan–Feb 1790, nom. illeg., non Molinaea Juss. (1789) nec Molinia Schrank (1789).—Type: M. racemosa Cav., nom. superf. [H. benghalensis (L.) Kurz].
Shrubs or woody vines climbing to 30 m. Leaves decussate; petiole eglandular or biglandular at apex; lamina eglandular or (usually) bearing 2 or more glands on margin or on abaxal surface set in slightly from margin; stipules small, triangular, borne on stem between petioles, persistent or deciduous, occasionally minute or apparently lacking. Inflorescences lateral or terminal, elongated (occasionally condensed) pseudoracemes, the flowers proximally decussate, distally decussate or (usually) in no particular order; pseudoracemes sometimes arranged in terminal leafless panicles; bracts and bracteoles eglandular, persistent or deciduous; floriferous peduncle well developed. Flowers bilaterally symmetrical in all whorls with the symmetry found in New World Malpighiaceae (see Family Description). Sepals leaving petals exposed during enlargement of bud, spreading in anthesis, mostly bearing 1 large, often decurrent gland below the posterior petal and between the 2 adjacent sepals (all sepals eglandular in 1 species; calyx glands very small and borne in 1–5 adjacent pairs in a few species); petals white or pink except the posterior petal (± different from the lateral 4) often proximally yellow, mostly densely sericeous abaxially (only sparsely sericeous proximally in 1 species), adaxially glabrous; stamens 10, all fertile; filaments connate at base, the 1 opposite anterior sepal much longer and stouter than the others and generally curved toward posterior petal, the other 9 alike or longer opposite sepals than opposite petals; anther mostly largest on the long filament, the other 9 alike or larger opposite sepals than opposite petals, glabrous; pollen globally symmetrical, without colpi, the pores 5–8, randomly distributed; receptacle glabrous on both sides of stamens; gynoecium 3-carpellate, the carpels all fertile, connate their whole length in ovary; style 1, on anterior carpel, curved toward posterior petal with the apex dorsally rounded, the stigma internal or terminal but bent inward. Fruit dry, breaking apart into samaras separating from a pyramidal torus; samara bearing 3 elongated lateral wings much longer than wide, 1 straddling the plane of symmetry at apex of carpel, the other 2 shorter, 1 on each side of plane of symmetry; dorsal wing usually lacking, occasionally 1, elongated, much shorter than lateral wings; ventral areole ovate or orbicular; carpophore absent. Chromosome number: n = 28, 29, or 30 (Bir et al., 1982; Devar, 1981; Devar & Boraiah, 1981; Gill et al., 1979, 1990; Pal, 1964; Sandhu & Mann, 1988).
25 species, possibly more, in forests of tropical southeastern Asia from Pakistan and India to Taiwan, the Philippines, and Indonesia. [map]
Hiptage is one of the largest Old World genera of Malpighiaceae, and because of its peculiar samara it is surely the easiest Asian genus to recognize. Nothing like that three-winged samara exists in any other branch of the family, in the New World or the Old World. A supposed similarity to the three-lobed samara of the West Indian group Triopterys (Mascagnia sens. lat.) is only apparent—in Triopterys the lobes of the single lateral wing are two up and one down, whereas in Hiptage the three completely distinct lateral wings are one up and two down (see the drawings: Hiptage, Triopterys). The newest phylogenetic tree (Davis & Anderson, 2010 [pdf]) places Hiptage without precision among a group of genera with lateral-winged samaras, as one would expect, and it is not difficult to imagine the long narrow side wings of the samara in Hiptage evolving from the lateral wings of a butterfly-shaped samara, but that leaves the apical wing in Hiptage unexplained. That wing seems unlikely to represent a displaced dorsal wing, because while most specimens lack a dorsal wing on the samara, some do have a small narrow dorsal wing on the dorsal rib, exactly where one would expect a dorsal wing to develop.
Hiptage is also notable for having one long stamen and nine short ones, and only one style that bends with the long stamen such that an insect that touches one will surely touch the other. The single large decurrent calyx gland is diagnostic when present, but it is not found in all species. Indeed, the fact that a few species have rudimentary paired calyx glands in the positions where they would be expected in a New World malpigh points to the likely source of the elongated commissural calyx gland found in most species of Hiptage—it is presumably the result of fusion of two neighboring glands, followed by enlargement.
Reference: Niedenzu, 1928.
Uses: Hiptage benghalensis is cultivated as an ornamental in warm areas around the world; the showy flowers are pleasantly fragrant. The species is thought to be native from India and Sri Lanka to the Philippines (Niedenzu, 1928), but it is difficult to know its true natural range because it has been cultivated for a long time and escapes readily, spreading aggressively and becoming a serious pest (Langeland et al., 2008).