Arcoa

Taxonomy

Arcoa I. Urban Repert. Spec. Nov. Regni Veg. 19: 4. 1 Mar 1923.

Subfamily: Caesalpinioideae.
Phylogenetic Number: 1.1.44.
Tribe: Caesalpinieae.
Group: Dimorphandra.
Species Studied - Species in Genus: 1 studied; 1 in genus.

Description

Fruit: A legume; unilocular; 2–3.5 cm long; 1.3–2 cm wide; 1–2 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 oblong to obovate; not inflated; 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; fleshy, or ligneous (fleshy when fresh, subligneous when dry); seed chambers externally invisible; margin not constricted; margin without sulcus; margin plain; wing(s) absent; nonstipitate; indehiscent. Replum invisible. Epicarp dull; monochrome; reddish brown; with surface texture uniform; densely covered with minute reddish glabrate; with hairs erect; with simple hairs (velvety); eglandular; without spines; not smooth; with elevated features; not veined; not tuberculate; shagreen; not exfoliating; without cracks; without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp present; surface not veined; 2-layered; without balsamic vesicles; with fibers; without reniform canals; with fibers over spongy tissue (thick); ligneous. Endocarp present; visible; glossy; opaque; monochrome; brown; without adhering pieces of testa; septate; not exfoliating; remaining fused to mesocarp and epicarp; entire. Seed(s) 1–6; length transverse to fruit length; neither overlapping nor touching; in 1 series. Funiculus 0.1–0.9 mm long; of 1 length only; filiform; straight. Aril absent.

Seed: 6–7 mm long; 4.3–5.5 mm wide; 1.5–2 mm thick; not overgrown; not angular; symmetrical; ovate (and emarginate); 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; brown; glabrous; not smooth; with elevated features, or recessed features; irregularly faintly tuberculate; minutely striate; osseous. Pleurogram absent. Pseudopleurogram absent. Fracture lines absent. Rim absent. Wing(s) absent. Raphe not visible. Hilum present; fully concealed; concealed by funicular remnant; without faboid split; punctiform; subapical to radicle tip; deeply recessed; not within corona, halo, or rim. Lens not discernible. Endosperm present; thick; not pluglike and not resembling tip of radicle. 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; with lobes; with lobes not touching; 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.

Distribution

Santo Domingo.

New World; West Indies (Santo Domingo).

Generic Notes

Only insect-Damaged material was available. Watson and Dallwitz (1983) described the fruit as "not internally septate".