Dialium

Taxonomy

Dialium C. Linnaeus Syst. Nat. ed. 12. 2: 56; Mant.: 3, 24. 15–31 Oct 1767.

Subfamily: Caesalpinioideae.
Phylogenetic Number: 1.2.03.
Tribe: Cassieae.
Subtribe: Dialiinae.
Species Studied - Species in Genus: 17 studied; ca. 40 in genus.

Description

Fruit: A legume; unilocular; 1–75 cm long; 1–75 cm wide; 0.8–60 cm thick; length less than twice as long as width; with deciduous androecial sheath; with deciduous corolla; with deciduous calyx; without orifice formed by curving of fruit or fruit segments; straight; not plicate; not twisted; asymmetrical; ovate, or elliptic, or circular; not inflated; compressed to terete; without beak; tapered at apex; aligned with longitudinal axis of fruit; rounded at base; aligned with longitudinal axis of fruit; with the apex and base uniform in texture; drupaceous, or ligneous (drupaceous when fresh or ligneous when dry); seed chambers externally invisible; margin not constricted; margin without sulcus; margin plain; wing(s) absent; stipitate to substipitate; with the stipe 1–10 mm long; indehiscent. Replum invisible. Epicarp dull; monochrome; tan to black, or red; with surface texture uniform; glabrous to pubescent and indurate; with hairs erect; with simple hairs; eglandular; without spines; not smooth; with elevated features; not veined; not tuberculate; shagreen (and often ruptered); not exfoliating (but brittle); without cracks; without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp present; surface not veined; 2-layered; without balsamic vesicles; without fibers; without reniform canals; with solid layer over spongy layer (pulpy when fresh); ligneous. Endocarp present; visible; dull; opaque; monochrome; dark brown; without adhering pieces of testa; nonseptate; not exfoliating; remaining fused to mesocarp and epicarp; entire. Seed(s) 1–2; length oblique to fruit length; neither overlapping nor touching; in 1 series. Funiculus 0.1–2 mm long; of 1 length only; thick; straight. Aril absent.

Seed: 7–50 mm long; 5–40 mm wide; 3–35 mm thick; not overgrown; not angular; symmetrical, or asymmetrical; ovate to circular, or irregular (slightly); compressed (often concaved in center of each face); 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; glossy to dull (absent in D. modestum); not modified by a bloom; colored; monochrome, or bichrome, or mottled; brown; glabrous; smooth, or not smooth; with elevated features; shagreen (if cuticle blistered); osseous. Pleurogram absent. Pseudopleurogram absent. Fracture lines present; longitudinal (conspicuous and curving from hilum to lens). Rim absent. Wing(s) absent. Raphe not visible (?). Hilum present; fully concealed; concealed by funicular remnant; without faboid split; punctiform; subapical to radicle tip; flush; not within corona, halo, or rim. Lens discernible (90–170 degrees from hilum); 1.5 mm long; with margins curved; elliptic; not in groove of raphe; recessed; dissimilar color from testa; black; not within corona, halo, or rim. Endosperm present; thick; not pluglike and not resembling tip of radicle; adnate to embryo. Cotyledons smooth; both outer faces convex; both the same thickness; thicker 1 longer than other; not folded; margin entire 180 degrees from base of radicle; similar at apex; partially concealing radicle; with lobes (one lobe longer than the other); with lobes not touching; with the interface division terminating at base of radicle; without margins recessed; green to white; 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 to moderately developed; glabrous.

Distribution

Generic Notes

Fruit characters are used to circumscribe the genus (Coetzer and Ross, 1976a). The epicarps of pressed fruits are usually broken because of a gap formed when the inner mesocarp layer shrinks. The pulpy mesocarp, the endocarp of Irwin and Barneby (1981), is acid "and is chewed to relieve thirst or macerated in cold water and used as a beverage" (Hutchinson and Dalziel, 1937). J.P. Rojo is revising Dialium (Lewis, pers. commun., 1988).