Trifidacanthus

Taxonomy

Trifidacanthus E.D. Merrill Philipp. J. Sci., Bot. 12: 269. Sep 1917.

Subfamily: Faboideae.
Phylogenetic Number: 3.11.05.
Tribe: Desmodieae.
Subtribe: Desmodiinae.
Species Studied - Species in Genus: 1 studied; 1 in genus.

Description

Fruit: A lomentloment:
usually dry fruit derived from a single carpel that breaks transversely into one-seeded fruit segments
(or a lomentloment:
usually dry fruit derived from a single carpel that breaks transversely into one-seeded fruit segments
segment) (with 3–7 articles, Ohashi et al., 1996); 2–6 cm long (loment with 3–7 articles, Ohashi et al., 1996); 0.5–0.7 cm wide; 0.055–0.057 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, or curved (slightly); not plicate; not twisted; asymmetrical; moniliform; 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, or declined; 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; membranous; seed chambers externally visible; seed chambers with the raised seed chambers not torulose; margin constricted; margin constricted on 1 margin and slightly constricted on the other margin; margin without sulcus; margin plain; wing(s) absent; stipitate; with the stipe 9–25 mm long; indehiscent. Replum invisible. Lomentloment:
usually dry fruit derived from a single carpel that breaks transversely into one-seeded fruit segments
an intact article; indehiscent; segments (articles) inconspicuous; segments (articles) 2.5–10 mm long; segments (articles) widest across seed area; segments (articles) with all essentially similar in shape; segments (articles) D-shaped, or oblong, or quadrangular. Epicarp dull; monochrome; brown, or tan; with surface texture uniform; pubescent and indurate; with hairs erect; with 1 type of pubescence; puberulent; 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 absent. Endocarp present; visible; dull; opaque; monochrome; reddish brown; smooth; without adhering pieces of testa; septate; with septa thicker than paper, firm; with septa eglandular; chartaceous; not exfoliating; remaining fused to epicarp; without wings; entire. Seed(s) 3–8; length parallel with fruit length; neither overlapping nor touching; in 1 series. Funiculus of 1 length only; triangular; straight. Aril present; dry; when dry rim-aril; entire; reddish brown.

Seed: 2–4.5 mm long; 1–1.4 mm wide; 0.7–0.8 mm thick; not overgrown; not angular; asymmetrical; reniform; 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; without pieces of adhering epicarp; not adhering to endocarp; free from endocarp; dull; not modified by a bloom; colored; monochrome; reddish brown; glabrous; smooth; coriaceous. Pleurogram absent. Pseudopleurogram absent. Fracture lines absent. Rim absent. Wing(s) absent. Raphe not visible. 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; 0.4 mm long; with curved outline; elliptic; marginal according to radicle tip, or between cotyledon and radicle lobe; recessed; not within corona, halo, or rim. Lens discernible; 0.5 mm long; with margins straight; linear; not in groove of raphe; confluent with hilum; recessed; dissimilar color from testa; darker than testa; black; not within corona, halo, or rim. 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; inner face flat. Embryonic axis deflexed; parallel to length of seed; without a joint evident between the radicle and the cotyledons. Radicle differentiated from cotyledon; linear; lobe tip straight; oblique to cotyledons; centered between cotyledons; less than 1/2 length of cotyledons. Plumule rudimentary.

Distribution

Vietnam, Hainan, Philippines, and Lesser Sunda Islands.

Old World; Indochina to China to Indonesia and the Philippines (Philippines, Lesser Sunda Islands, Indochina (Vietnam, Hainan)).

Generic Notes

Merrill (1917) founded the genus without seeing fruits, and two years later he described the fruits (Merrill, 1919). Ohashi et al. (1996) revised the genus and concluded that it is a distinct, montypic genus in tribe Desmodieae.

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).