Zygia

Taxonomy

Zygia P. Browne Civ. Nat. Hist. Jamaica 279. 10 Mar 1756.

Subfamily: Mimosoideae.
Phylogenetic Number: 2.5.20.
Tribe: Ingeae.
Species Studied - Species in Genus: 5 studied; ca. 60 in genus.

Description

Fruit: A legumelegume:
usually dry, dehiscent fruit derived from a single carpel that opens along two longitudinal sutures
; unilocular; 5–45 cm long; 1.2–2.5 cm wide; 1 cm thick; 2–9 times longer than wide, or more than 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, or curved, or 1-coiled; not plicate; not twisted; asymmetrical, or symmetrical; oblong, or falcate; with both sutures parallelly curved; not inflated; flattened to compressed; without beak; rounded at apex; aligned with longitudinal axis of fruit; rounded at base to tapered at base; aligned with longitudinal axis of fruit, or oblique with longitudinal axis of fruit; with the apex and base uniform in texture; leathery, or ligneous; seed chambers externally faintly visible; margin not constricted to constricted; margin constricted along both margins; margin without sulcus; margin plain; wing(s) absent; nonstipitate to substipitate; tardily with all layers dehiscing; splitting along suture(s). Dehiscence of valves along 1 suture; apical and down; active; with valves reflexing (along ventral margin, remaining attached to sutures). Replum invisible. Epicarp dull; monochrome; brown; with surface texture uniform; minutely pubescent and indurate to glabrate, or glabrous; with hairs erect; with simple hairs; eglandular; without spines; smooth, or not smooth; with elevated features; not veined; not tuberculate; shagreen; not exfoliating; without cracks, or with cracks (rarely); cracking transverse to fruit length; 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; mealy and fibrous throughout; ligneous. Endocarp present; visible; dull; opaque; monochrome; reddish brown; smooth; without adhering pieces of testa; nonseptate, or septate (rarely); not exfoliating; remaining fused to mesocarp and epicarp; entire. Seed(s) 2–12; length transverse to fruit length; neither overlapping nor touching, or touching (especially when large); in 1 series. Funiculus 3–4 mm long; of 1 length only; thick; curved. Aril absent.

Seed: 15–25 mm long; 13–20 mm wide; 5–7 mm thick; not overgrown; not angular; symmetrical; irregular to circular, or oblong, or elliptic (rarely); 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; without pieces of adhering epicarp; not adhering to endocarp; free from endocarp; dull, or glossy; not modified by a bloom; colored; monochrome; brown; glabrous; smooth, or not smooth; with elevated features; rugose and shagreen; coriaceous, or chartaceous. Pleurogram absent. Pseudopleurogram absent. Fracture lines absent. Rim present; wing-like narrowly around seed. Wing(s) absent. Raphe not visible. Hilum present; visible; without faboid split; punctiform; subapical to radicle tip to apical at apex of radicle tip; recessed; not within corona, halo, or rim. Lens discernible; 2 mm long; with margins curved; elliptic; not in groove of raphe; recessed (a pit); same color as testa; brown; 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; 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; straight with embryonic axis; centered between cotyledons. Plumule well developed; densely pubescent.

Distribution

Mexico, Central America, Greater Antilles, and tropical South America.

New World; Mexico, West Indies, Central America, and South America (tropical); Argentina, Peru, Brazil, Ecuador, and the Guianas.

Generic Notes

At least Z. latifolia has concaved cotyledon faces (E) similar to the faces found in Entada gigas (3.13). Polhill (1994b) accepted Marmaroxylon E.P. Killip (2.5.21), but it was included in Zygia (2.5.20) as a section by Barneby and Grimes (1997) whom we are following. The species count follows Barneby and Grimes.