Subfamily: Caesalpinioideae.
Phylogenetic Number: 1.4.21.
Tribe: Detarieae.
Group: Hymenostegia.
Species Studied - Species in Genus: 5 studied; ca. 3 in genus.
Fruit: A legume; unilocular; 7–25 cm long; 3–8.5 cm wide; 0.8–1.3 cm thick; 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; not plicate; not twisted; symmetrical, or asymmetrical; linear to oblong; with 1 straight and 1 curved suture; widest near middle or D-shaped; not inflated; compressed; without beak; long tapered at apex to tapered at apex; aligned with longitudinal axis of fruit to oblique with longitudinal axis of fruit; rounded at base; aligned with longitudinal axis of fruit to right angled with longitudinal axis of fruit; with the apex and base uniform in texture; coriaceous; seed chambers externally visible; margin not constricted; margin without sulcus; margin embellished; margin with thickened sutural areas (usually ventral margin); wing(s) absent; substipitate; with all layers dehiscing; splitting along suture(s). Dehiscence of valves along both sutures. Replum invisible. Epicarp dull; monochrome; brown to black; with surface texture uniform; glabrous; eglandular; without spines; not smooth; with elevated features; veined; transversely veined relative to fruit length; not tuberculate; 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; with fibers; without reniform canals; mealy; ligneous. Endocarp present; visible; dull; opaque; monochrome; brown; scurfy; without adhering pieces of testa; subseptate; not exfoliating; remaining fused to mesocarp and epicarp; entire. Seed(s) 1–8; length transverse to fruit length; neither overlapping nor touching; in 1 series. Funiculus 0.1–6 mm long; of 1 length only; thick; straight. Aril absent (arillike funicular remnant in I. bijuga).
Seed: (15–)20–43 mm long; (10–)17–35 mm wide; 7–11 mm thick; not overgrown; angular, or not angular; symmetrical; elliptic to ovate, or oblong, or triangular to quadrangular; compressed; 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; without pieces of adhering epicarp; not adhering to endocarp; free from endocarp; dull; not modified by a bloom; colored; monochrome; black (with patches of reddish brown to yellow brown scurf from endocarp); glabrous; smooth; osseous. Pleurogram absent. Pseudopleurogram absent. Fracture lines absent. Rim absent. Wing(s) absent. Raphe not visible. Hilum present; visible, or fully concealed; concealed by funicular remnant; without faboid split; larger than punctiform; 0.1–1.5 mm long; with straight outline; apical at apex of radicle tip; flush; not within corona, halo, or rim. Lens discernible, or not discernible; 2 mm long (180 degrees from hilum); with margins curved; circular; not in groove of raphe; mounded; same color as testa; not within corona, halo, or rim. Endosperm absent. Cotyledons smooth; both outer faces convex; both the same thickness; both more or less of equal length; not folded; margin entire 180 degrees from base of radicle; similar at apex; partially concealing radicle (only tip exposed); notched at radicle and split 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; centered between cotyledons. Plumule rudimentary; glabrous.
Seed, cotyledon, embryo, and testa: I. bijuga (Colebrooke) C.E.O. Kuntze - top left center seed topography, far left cotyledon split and notched and concealing all but tip of radicle (above) and embryonic axis (below), bottom left center seeds, testa SEMs; I. palembanica F.A.W. Miquel - left center seed topography.
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