Xanthocercis

Taxonomy

Xanthocercis H.E. Baillon Adansonia 9: 293. 20 Apr 1870.

Subfamily: Faboideae.
Phylogenetic Number: 3.2.14.
Tribe: Sophoreae.
Group: Angylocalyx.
Species Studied - Species in Genus: 2 studied; 3 in genus.

Description

Fruit: A legumelegume:
usually dry, dehiscent fruit derived from a single carpel that opens along two longitudinal sutures
; unilocular; 2.7–5.4(–9) cm long; 1.5–2.5 cm wide; 1–2.1 cm thick; 2–9 times longer than wide; with deciduous androecial sheath; with deciduous corolla; with persistent calyx, or deciduous calyx; with calyx shorter than fruit; without orifice formed by curving of fruit or fruit segments; straight; not plicate; not twisted; symmetrical; elliptic to fusiform; inflated, or not inflated; terete; with beak, or without beak; straight to declined; with solid beak the same color and texture as fruit; rounded at apex, or short tapered at apex; aligned with longitudinal axis of fruit, or oblique 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 invisible; margin not constricted, or constricted; margin slightly constricted along both margins; margin without sulcus; margin plain; wing(s) absent; stipitate, or substipitate; with the stipe 1–20 mm long; indehiscent. Epicarp dull; monochrome; green to yellow; with surface texture uniform; glabrous; eglandular; without spines; not smooth; with recessed features; pitted; 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; monochrome; white; fibrous; without adhering pieces of testa; nonseptate; coriaceous; not exfoliating; remaining fused to mesocarp and epicarp; without wings; entire. Seed(s) 1–2(–3); length parallel with fruit length. Funiculus ca. 1 mm long; thick; straight. Aril present; dry; when dry rim-aril; entire; cream.

Seed: 14–25 mm long; 10–15 mm wide; 8–12 mm thick; not overgrown; not angular; symmetrical, or asymmetrical; oblong to ovate, or irregular, or reniform; terete; with surface smooth; without visible radicle and cotyledon lobes; with shallow 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, or mottled; with infrequent mottles; black, or blue, or brown (dark, when mottled); with brown overlay (lighter); glabrous; smooth, or not smooth; with elevated features; wrinkled; coriaceous. Pleurogram absent. Pseudopleurogram absent. Fracture lines absent. Rim absent. Wing(s) absent. Raphe visible, or not visible; from hilum through lens to base of seed and terminating; not bifurcating; color of testa; flush, or raised (slightly). Hilum present; visible; with faboid split; with the lips of the faboid split the same color as the rest of the hilum; larger than punctiform; 2–2.5 mm long; with curved outline; elliptic to fusiform; apical according to radicle tip but marginal according to seed length; recessed; within halo; halo lighter than testa. Lens discernible; 3–4 mm long; with margins straight; linear; not in groove of raphe; confluent with hilum; flush; same color as testa, or similar color as testa; lighter than testa; brown; within halo; halo color lighter than testa. Endosperm present; thin; not pluglike and not resembling tip of radicle; covering entire embryo; adnate to testa and embryo. Cotyledons smooth; both outer faces convex; both the same thickness; both more or less of equal length; with both folded, or not folded; sufficiently folded for inner face to touch itself; portions of inner folded face unequal; margin entire 180 degrees from base of radicle; similar at apex; partially concealing radicle, or not concealing radicle; notched at radicle; without lobes; with margin(s) recessed, or without margins recessed; with both margins recessed; yellow; inner face flat; glabrous on inner face. Embryonic axis straight; oblique to length of seed, or parallel to length of seed; without a joint evident between the radicle and the cotyledons. Radicle differentiated from cotyledon; bulbose, or triangular; lobe tip straight; straight with embryonic axis; centered between cotyledons; less than 1/2 length of cotyledons. Plumule rudimentary; glabrous.

Distribution

Northern Madagascar (1 sp.) and south-central to southern Africa (1 sp.).

Old World; Africa and Madagascar.

Generic Notes

Van der Maesen (1997) described a new species, X. rabiensis L.J.G. van der Maesen, from Gabon which was included in the species count.

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.