Sweetia

Taxonomy

Sweetia C.P.J. Sprengel Nom. cons. Syst. Veg. 2: 171, 213. Jan-Mai 1825.

Subfamily: Faboideae.
Phylogenetic Number: 3.2.02.
Tribe: Sophoreae.
Group: Myroxylon.
Species Studied - Species in Genus: 1 studied; 1 in genus.

Description

Fruit: A legumelegume:
usually dry, dehiscent fruit derived from a single carpel that opens along two longitudinal sutures
; unilocular; 4.5–6 cm long; 1–1.3 cm wide; 0.2–0.3 cm thick; 2–9 times longer than wide; with deciduous androecial sheath; with deciduous corolla; with persistent calyx; with calyx shorter than fruit; without orifice formed by curving of fruit or fruit segments; straight; not plicate; not twisted; asymmetrical; samaroid; with both sutures unequally curved; not inflated; compressed; without beak; rounded at apex; aligned with longitudinal axis of fruit, or oblique with longitudinal axis of fruit (slightly); rounded at base; aligned with longitudinal axis of fruit; with the apex and base uniform in texture; chartaceous; seed chambers externally visible; margin not constricted; margin without sulcus; margin plain, or embellished; margin with wing(s); wing(s) present; wing(s) 1; wing(s) 30–35 mm wide; wing(s) samaroid; wing(s) apical; substipitate; with the stipe 3–4 mm long; indehiscent. Epicarp dull; monochrome, or multicolored; mottled; brown to tan; with brown overlay; mottling color combination variable; with surface texture uniform; glabrous; eglandular; without spines; not smooth; with elevated features; veined; irregularly veined; not tuberculate; wrinkled; not exfoliating; without cracks; without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp present; thin; surface not veined; 1-layered; without balsamic vesicles; without fibers; without reniform canals; solid; chartaceous. Endocarp present; visible; dull; opaque; mottled; white; with mottling more or less uniform (dark); with tan overlay; scurfy; without adhering pieces of testa; nonseptate; chartaceous; not exfoliating; remaining fused to mesocarp and epicarp; with wing(s) extending into epicarp; entire. Seed(s) 1; length parallel with fruit length. Funiculus ca. 0.5 mm long; flattened; straight. Aril absent.

Seed: 13–15 mm long; 4–5 mm wide; 1.5–2 mm thick; not overgrown; angular; asymmetrical; irregular to samaroid; 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; with pieces of adhering epicarp, or 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; wrinkled; chartaceous. Pleurogram absent. Pseudopleurogram absent. Fracture lines absent. Rim absent. Wing(s) absent. Raphe not visible. Hilum present; fully concealed; concealed by funicular remnant; larger than punctiform; 0.8–1.4 mm long; with curved outline; fusiform; subapical to radicle tip; flush; not within corona, halo, or rim. Lens not discernible. 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; split over radicle; with lobes (small); with lobes not touching; without basal groin formed by lobes; with the interface division terminating at base of radicle; without margins recessed; brown; inner face flat; glabrous on inner face. Embryonic axis oblique; oblique to length of seed; without a joint evident between the radicle and the cotyledons. Radicle differentiated from cotyledon; triangular; lobe tip straight; oblique to cotyledons; centered between cotyledons; less than 1/2 length of cotyledons. Plumule moderately developed; glabrous.

Distribution

Brazil, Bolivia, and Paraguay.

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

Generic Notes

Following Yakovlev (1969) we recognize Sweetia with only one species. The remaining species belong in Acosmium (2.01).

Tribal Notes

Tribe Sophoreae

Polhill (1981b) stated that the Sophoreae s.l. is a tribe of convenience between the Caesalpinioideae and the bulk of the Papilionoideae, sharply defined from neither. He transferred four genera from Sophoreae into the Swartzieae (1), Amburana (3.1.15), Ateleia (3.1.13), Cyathostegia (3.1.14), and Holocalyx (3.1.12), following Herendeen's (1995) cladistic analyses. Herendeen performed cladistic analyses for all Swartzieae genera, sensu Cowan (1981), 19 Sophoreae genera, and three Caesalpinioideae genera. He concluded that Swartzieae is polyphyletic and that it should be disbanded and its genera transferred to Sophoreae. Preliminary rbcL data (Doyle et al. 1997) supported his conclusions.