Arthroclianthus

Taxonomy

Arthroclianthus H.E. Baillon Adansonia 9: 296. 20 Apr 1870.

Subfamily: Faboideae.
Phylogenetic Number: 3.11.03.
Tribe: Desmodieae.
Subtribe: Desmodiinae.
Species Studied - Species in Genus: 13 studied; ca. 10 in genus.

Description

Fruit: A loment (or a loment segment); 8–14 cm long; 0.5–1.2 cm wide; 0.1–1.15 cm thick; more than 9 times longer than wide, or 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, or curved (slightly); not plicate; not twisted; asymmetrical, or symmetrical; moniliform (some with elongated isthmuses), or linear; with 1 straight and 1 curved suture, or both sutures parallelly curved; narrowing in several places, resembling Desmodium (3.11.09) fruit; not inflated; flattened; with beak; straight; with solid beak the same color and texture as fruit; 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; seed chambers with the raised seed chambers not torulose; margin constricted; margin constricted along both margins; margin without sulcus; margin plain; wing(s) absent; stipitate; with the stipe 14–40 mm long; indehiscent. Replum invisible. Loment indehiscent; segments (articles) inconspicuous; segments (articles) 14–35 mm long; segments (articles) widest across seed area; segments (articles) with all essentially similar in shape; segments (articles) D-shaped, or oblong. Epicarp dull; monochrome; greenish brown to brown; with surface texture uniform; pubescent and indurate, or glabrous; with hairs erect; with 1 type of pubescence; pilose; with pubescence gray; with pubescence uniformly distributed; with simple hairs; pliable; with hair bases plain; 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 present; thin; surface uniformly veined; 1-layered; without balsamic vesicles; without fibers; without reniform canals; solid; coriaceous. Endocarp present; visible; glossy; opaque; monochrome; greenish tan; smooth; without adhering pieces of testa; septate; with septa thicker than paper, firm; with septa eglandular; chartaceous; not exfoliating; remaining fused to mesocarp and epicarp; without wings; entire. Seed(s) 4–9; length parallel with fruit length; neither overlapping nor touching; in 1 series. Funiculus of 1 length only; triangular; straight. Aril absent.

Seed: 7–9 mm long; 4–4.5 mm wide; 0.4–0.5 mm thick; not overgrown; not angular; asymmetrical; reniform (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; dull; not modified by a bloom; colored; monochrome; reddish brown; glabrous; smooth; chartaceous. Pleurogram absent. Pseudopleurogram absent. Fracture lines absent. Rim absent. Wing(s) absent. Raphe visible; from hilum to lens (near base of seed); not bifurcating; darker than testa; dark reddish brown; raised. Hilum present; fully concealed; concealed by funicular remnant; without faboid split; punctiform; marginal according to radicle tip; flush; within rim; rim color darker than testa. Lens discernible; with margins curved; circular; not in groove of raphe; adjacent to hilum; 2.5 mm from hilum (length of raphe); mounded; similar color as testa; darker than testa; dark reddish brown; not within corona, halo, or rim. 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; not concealing radicle; entire over radicle; without lobes; with the interface division terminating at base of radicle; without margins recessed; yellow; inner face flat; glabrous on inner face. Embryonic axis deflexed; oblique to length of seed; without a joint evident between the radicle and the cotyledons. Radicle differentiated from cotyledon; linear; deflexed and parallel to cotyledon length; centered between cotyledons; less than 1/2 length of cotyledons. Plumule moderately developed; glabrous.

Distribution

New Caledonia.

Old World; Pacific (New Caledonia).

Generic Notes

Hochreutiner (1907) monographed the genus, and Ohashi et al. (1981) noted that Arthroclianthus is scarcely distinct from Nephrodesmus 11.04). We are unable to ascertain which ca. ten species Ohashi et al. recognized.

Tribal Notes

Tribe Desmodieae

Ohashi et al. (1981) started their treatment of the Desmodieae with these thoughts: "A sensible classification of Desmodieae is prejudiced by the traditional over-weighting of fruit characters." (sic) "The fruit normally consists of indehiscent jointed articles, but fruits that open have arisen at least seven times..." They supplemented their text with a fruit-seed plate. They placed Brya and Cranocarpus (11.02), the only two New World endemic genera, in the new subtribe Bryinae, "characterized most notably by glochidiate hairs." Bailey et al. (1997), using the chloroplast rpl2 intron and ORF184, suggested that Brya, Cranocarpus, Phylacium (11.22), and Neocollettia (11.26) are not members of Desmodieae and that they probably belong in Aeschynomeneae (14).