Mimozyganthus

Taxonomy

Mimozyganthus A.E. Burkart Darwiniana 3: 448. 15 Dec 1939.

Subfamily: Mimosoideae.
Phylogenetic Number: 2.2.01.
Tribe: Mimozygantheae.
Species Studied - Species in Genus: 1 studied; 1 in genus.

Description

Fruit: A legume; unilocular; 2–3.5 cm long; 0.8–1.5 cm wide; 0.1–0.2 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; not plicate; not twisted; asymmetrical; elliptic to obovate; not inflated; flattened; without beak; short tapered at apex to rounded at apex; aligned with longitudinal axis of fruit; short tapered at base; aligned with longitudinal axis of fruit; with the apex and base uniform in texture; coriaceous; seed chambers externally visible; margin not constricted (but ventral margin curved and wider than straighter dorsal margin); margin without sulcus; margin plain; wing(s) absent; stipitate; with the stipe 3–6 mm long; indehiscent. Replum invisible. Epicarp dull; monochrome; tan; with surface texture uniform; glabrous; eglandular; without spines; not smooth; with elevated features; veined; reticulately veined; not tuberculate; not exfoliating; without cracks; without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp absent. Endocarp present; visible; dull; opaque; monochrome; pale tan; smooth; without adhering pieces of testa; nonseptate; not exfoliating; entire. Seed(s) 1–2; length oblique to fruit length; neither overlapping nor touching; in 1 series. Funiculus 5–6 mm long; of 1 length only; filiform; S-curved. Aril absent.

Seed: 5.2–7.3 mm long; 5.4–7.5 mm wide; 1–1.8 mm thick; not overgrown; not angular; symmetrical, or asymmetrical; ovate to circular, or trapezoid (sub); 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; glossy; not modified by a bloom; colored; monochrome; medium to dark brown, or gray (brownish); glabrous; not smooth; with elevated features; rugose; coriaceous. Pleurogram absent. Pseudopleurogram absent. Fracture lines absent. Rim absent. Wing(s) absent. Raphe 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; up to 0.4 mm long; with margins straight; irregular; not in groove of raphe; flush; dissimilar color from testa; lighter than testa; tan; 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; partially concealing radicle; with lobes; with lobes touching (auriculate); without basal groin formed by lobes; 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; glabrous.

Distribution

Argentina and western Paraguay.

New World; South America (Argentina and Paraguay); Argentina and Brazil.

Generic Notes

Burkart (1939a) monographed the genus. Placement of the monotypic genus Dinizia W.A. Ducke of Brazil and Guyana in this tribe has been discussed, evaluated, and rejected by Elias (1981), who did not cite fruit and seed characters. Fruit and seed characters support his decision. The short (5 mm or less in length) stipe is so clearly discernible that the fruits are not described as substipitate. The micropyle remains open in mature seeds.