Inga

Taxonomy

Inga P. Miller Gard. Dict. Abr. ed. 4. 28 Jan 1754.

Subfamily: Mimosoideae.
Phylogenetic Number: 2.5.01.
Tribe: Ingeae.
Species Studied - Species in Genus: 29 studied; ca. 300 in genus.

Description

Fruit: A legume; unilocular; 1.5–65 cm long; 1–8.5 cm wide; 0.8–3 cm thick; length less than twice as long as width, or 2–9 times longer than wide; with deciduous androecial sheath; with deciduous corolla; with deciduous calyx; without orifice formed by curving of fruit or fruit segments; straight to curved to 2-coiled; not plicate; not twisted, or twisted; asymmetrical, or symmetrical; linear to oblong, or ovate, or falcate; with both sutures parallelly curved; not inflated; compressed to flattened, or terete (rarely), or quadrangular; without beak; rounded at apex to short tapered at apex; aligned with longitudinal axis of fruit; rounded at base; aligned with longitudinal axis of fruit, or oblique with longitudinal axis of fruit; with the apex and base uniform in texture; coriaceous to ligneous; seed chambers externally visible, or invisible; margin not constricted to constricted; margin constricted along both margins, or slightly constricted along both margins; margin without sulcus; margin plain; wing(s) absent; stipitate, or nonstipitate, or substipitate (former species of Affonsea); with the stipe 5–20 mm long; indehiscent to with epicarp and mesocarp dehiscing and endocarp not dehiscing, or with all layers dehiscing (valves scarcely opening or bursting irregularly, with or without many ribs (many ribbed in I. edulis) or sunken and sutures enlarged creating winglike margins, remaining attached to sutures); splitting along suture(s). Dehiscence of valves passive. Replum invisible. Epicarp dull to glossy; monochrome; brown (the former species of Affonesa reddish (because of dense pubescence) then dark (after hairs fall)); with surface texture uniform; glabrous to pubescent and indurate (densely), or glabrate (often with age), or pubescent but soon deciduous (former species of Affonsea, densely reddish brown); with hairs erect; with simple hairs (short to long reddish to brownish or yellowish hairs); eglandular; without spines; not smooth; with rarely elevated features; veined; reticulately veined, or longitudinally veined relative to fruit length; not tuberculate; shagreen (former species of Affonsea, after hairs fall); not exfoliating; without cracks; without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp present; surface not veined; 1-layered; without balsamic vesicles; without reniform canals; fibrous throughout; ligneous. Endocarp present; visible; glossy, or dull (rarely, former species of Affonsea); opaque; monochrome; brown, or white (when falling away from fruit with seed), or tan (former species of Affonsea); smooth (when remaining with fruit), or pulpy; without adhering pieces of testa; septate, or nonseptate, or subseptate (former species of Affonsea); ligneous (when remaining within fruit), or pulpy (when falling free with seed as white sweet pulp and serving or not as surrogate testa); not exfoliating; remaining fused to mesocarp and epicarp, or separating from mesocarp; entire. Seed(s) 2–21; length transverse to fruit length to parallel with fruit length; neither overlapping nor touching; in 1 series. Funiculus 1–9 mm long; of 1 length only; thick to filiform; curved to straight, or triangular (former species of Affonsea). Aril absent.

Seed: 12–26 mm long; (6.5–)9–16 mm wide (narrowest seeds in former species of Affonsea); 2–16 mm thick; not overgrown; not angular to angular; symmetrical; oblong; compressed to flattened; with surface smooth; without visible radicle and cotyledon lobes; without hilar sinus; without umbo on seed faces; without medial ridge on each face. Cuticle not exfoliating; not inflated; not wrinkled. Testa present (either remaining attached to endocarp with embryo falling free or remaining attached to embryo and falling free of endocarp), or absent (rarely, former species of Affonsea, from mature embryos); without pieces of adhering epicarp; not adhering to endocarp; free from endocarp; dull; not modified by a bloom; colored; monochrome; brown to black; glabrous; smooth, or not smooth; with elevated features; shagreen; coriaceous to osseous. Pleurogram absent. Pseudopleurogram absent. Fracture lines absent. Rim present; wing-like around seed. Wing(s) absent. Raphe not visible. Hilum present; visible; without faboid split; punctiform; apical at apex of radicle tip, or subapical to radicle tip (rarely, former species of Affonsea); flush to recessed; not within corona, halo, or rim. Lens discernible, or not discernible (former species of Affonsea); 1.1–3 mm long; with margins curved; elliptic; not in groove of raphe; mounded; similar color as testa, or dissimilar color from testa; lighter than testa; tan (based on I. vera C.L. Willdenow subsp. affinis (A.P. de Candolle) T.D. Pennington); not within corona, halo, or rim. Endosperm absent. Cotyledons smooth; both outer faces flat; both the same thickness; both more or less of equal length; not folded; margin entire 180 degrees from base of radicle; similar at apex; completely concealing radicle, or partially concealing radicle; split over radicle, or entire over radicle; with the interface division terminating at base of radicle; without margins recessed; inner face flat; glabrous on inner face. Embryonic axis straight; parallel to length of seed; without a joint evident between the radicle and the cotyledons. Radicle differentiated from cotyledon; straight with embryonic axis; centered between cotyledons. Plumule rudimentary to well developed; pubescent (when well developed).

Distribution

Generic Notes

Pittier (1914–1917) monographed the genus, and Pennington (1997) recently did so. The number of species follows Pennington. Pennington synonymized Affonsea A.F.C.P. de Saint-Hilaire with Inga. Affonsea had been separated from Inga because it was multicarpellate, but Pennington discovered multicarpellate species unrelated to the former Affonsea and so united the two genera. Vinha (1981) monographed the former Affonsea species of southern Bahia, Brazil, and recognized 14 species, 6 new. Vinha saw no fruits of his new species. Bravato (1974) described I. coriacea (Persoon) Desvaux seeds as polyembryonic with irregular lobulate cotyledonss tightly encrusted one with the other. Several authors mistakenly noted that the aril becomes a surrogate testa and correctly noted that the seeds germinate through the rotting fruits. The aril is really the white, sweet, pulpy endocarp, which may serve as a surrogate testa.