Abrus

Taxonomy

Abrus M. Adanson Fam. 2: 327, 511. Jul-Aug 1763.

Subfamily: Faboideae.
Phylogenetic Number: 3.5.01.
Tribe: Abreae.
Species Studied - Species in Genus: 10 studied; 17 in genus.

Description

Fruit: A legume; unilocular; 3–4.5 cm long; 1–1 cm wide; 0.5–0.5 cm thick; 2–9 times longer than wide; with deciduous androecial sheath; with deciduous corolla; with deciduous calyx; straight; not plicate; not twisted; asymmetrical, or symmetrical; oblong; with 1 straight and 1 curved suture; widest near middle or D-shaped; not inflated; compressed; without beak; short tapered at apex; aligned with longitudinal axis of fruit, or right-angled with longitudinal axis of fruit; short tapered at base, or rounded at base; oblique with longitudinal axis of fruit (slightly); with the apex and base uniform in texture; coriaceous; seed chambers externally visible, or invisible; seed chambers with the raised seed chambers not torulose; margin not constricted; margin without sulcus; margin plain; wing(s) absent; substipitate; with all layers dehiscing; splitting along suture(s). Dehiscence of valves along 1 suture, or both sutures; apical and down; active; with valves twisting. Replum invisible. Epicarp dull; monochrome; tan; with surface texture uniform; pubescent but soon deciduous; with hairs erect; with 1 type of pubescence; puberulent; with pubescence gray-brown, or gray; with pubescence uniformly distributed; with simple hairs; pliable; with hair bases plain; eglandular; without spines; smooth (nearly); not veined; not tuberculate; checking; with cracks, or without cracks; cracking oblique to fruit length; without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp present; thin; 1-layered; without balsamic vesicles; without reniform canals; solid; ligneous (sub). Endocarp present; visible; dull; opaque; monochrome; tan, or white; smooth; without adhering pieces of testa; septate (fragile and conspicuously developed to slightly developed septa), or subseptate; with septa thin (tissue paper-like), flexible; with septa eglandular; coriaceous; not exfoliating (though somewhat in A. precatorius); remaining fused to mesocarp and epicarp; without wings; entire. Seed(s) 3–7; length oblique to fruit length (slightly); neither overlapping nor touching; in 1 series. Funiculus 2–3 mm long; of 1 length only; thick; straight, or hooked, or triangular. Aril present; fleshy, or dry; when fleshy annular; entire; covering less than 1/2 of seed; when dry tongue-aril; entire; tan.

Seed: 3.5–7 mm long; 2.3–5.5 mm wide; 1.8–5.5 mm thick; not overgrown; not angular; symmetrical (except hilum); oblong; terete (A. precatorius), or quadrangular; 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, or bichrome (A. precatorius black at hilum end and scarlet to dark reddish-brown at opposite end), or mottled, or streaked; with frequent mottles to infrequent mottles; with frequent streaks to infrequent streaks; black, or brown, or gray, or ivory, or olive, or orange, or red, or purple, or scarlet; with black overlay; glabrous; smooth, or not smooth (A. gorsei J. Berhart, A. canescens); with elevated features; shagreen; coriaceous. Pleurogram absent. Fracture lines absent. Rim absent. Raphe visible, or not visible; from hilum through lens to base of seed and terminating, or hilum to near base of seed and terminating; color of testa; flush. Hilum present; visible, or partially concealed; concealed by funicular remnant (A. canescens); with faboid split; with the lips of the faboid split the same color as the rest of the hilum, or lighter colored than the rest of the hilum and therefore conspicuous; larger than punctiform; 1.2–3 mm long; with curved outline, or straight outline; circular; oblong; subapical to radicle tip, or marginal according to radicle tip (A. canescens); recessed; within rim; rim color of testa (but duller). Lens discernible, or not discernible (A. fruticulosus N. Wallich ex R. Wight & G.A.W. Arnott); 0.5–2 mm long; with margins straight, or curved; irregular, or linear; irregular; not in groove of raphe; adjacent to hilum, or confluent with hilum; 0.1–1 mm from hilum; recessed; dissimilar color from testa; darker than testa; black; not within corona, halo, or rim. Endosperm present; thin; not pluglike and not resembling tip of radicle; covering entire embryo; adnate to testa. 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; not concealing radicle; entire over radicle; without lobes, or with lobes; with lobes not touching; without basal groin formed by lobes; with the interface division terminating at base of radicle; without margins recessed; white, or yellow; inner face flat; glabrous on inner face. Embryonic axis deflexed; parallel 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 well developed; glabrous

Distribution

Pantropic to pansubtropic.

New World and Old World; pantropical to pansubtropical; West Indies to Mexico to Central America to South America; Brazil and Ecuador; Southwest Asia to Africa to Madagascar to Indian Ocean to India to Indochina to China to Australia to Indonesia and the Philippines to Fiji to Macaronesia.

Generic Notes

Polhill (1981e, 1994a, 1994b) evaluated the placement of Abrus and concluded that the genus is best placed in its own monotypic tribe situated between the Dalbergieae and Amorpheae. Verdcourt (1970c) monographed Abrus, and in accepting this work, we reject Breteler (1960). Abrus precatorius has bicolored scarlet (red) and black seeds which are deadly poisonous when chewed (Gunn, 1969), and according to Verdcourt, A. aureus R. Viguier also has red and black seeds. Similarly colored seeds include Rhynchosia pyramidalis (10.80) and species of Ormosia (2.15). For additional micrographs of the testa, see Lersten and Gunn (1982). Because of human selection, seeds of A. precatorius range in color from bicolor (scarlet to dark red and black) to monochome brown, tan, yellow, and ivory.