Robinia

Taxonomy

Robinia C. Linnaeus Sp. Pl. 722. 1 Mai 1753.

Subfamily: Faboideae.
Phylogenetic Number: 3.8.07.
Tribe: Robinieae.
Group: Robinia.
Species Studied - Species in Genus: 4 studied; 4 in genus.

Description

Fruit: A legumelegume:
usually dry, dehiscent fruit derived from a single carpel that opens along two longitudinal sutures
; unilocular; 4.5–10 cm long; 0.8–1 cm wide; 0.2 cm thick; 2–9 times longer than wide; with deciduous androecial sheath; with deciduous corolla; with deciduous calyx; without orifice formed by curving of fruit or fruit segments; straight, or curved (slightly); not plicate; not twisted; symmetrical, or asymmetrical; linear; with both sutures nearly straight; not inflated; flattened, or compressed; without beak, or with beak; with solid beak the same color and texture as fruit; tapered 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 invisible, or visible; seed chambers with the raised seed chambers not torulose; margin not constricted, or constricted; margin constricted along both margins; margin without sulcus; margin plain, or embellished; margin with wing(s); wing(s) absent, or present (occasionally); wing(s) 1; wing(s) 0.1–0.2 mm wide; wing(s) sutural; wing(s) on 1 suture (upper); substipitate; with all layers dehiscing; splitting along suture(s). Dehiscence of valves along both sutures (lower suture first); apical and down; active; with valves twisting. Replum invisible. Epicarp dull; monochrome, or multicolored; streaked; brown (reddish); with red overlay; with surface texture uniform; glabrous, or 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; glandular; with glandular hairs; with spines; not smooth; with elevated features, or recessed features; veined, or not veined; reticulately veined (faintly and incompletely); tuberculate; warty, or tuberculate; slitted obliquely (minute); 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; coriaceous. Endocarp present; visible; dull; opaque; monochrome; tan; smooth; without adhering pieces of testa; septate, or nonseptate; with septa thicker than paper, firm; with septa eglandular; chartaceous; not exfoliating; remaining fused to mesocarp and epicarp; without wings, or with wing(s) extending into epicarp (occasionally); entire. Seed(s) 2–13; length transverse to fruit length; neither overlapping nor touching; in 1 series. Funiculus 0.5–1.5 mm long; of 1 length only; thick; straight, or curved (near hilum). Aril present; dry; when dry rim-aril; entire; tan.

Seed: 4–6 mm long; 3–3.5 mm wide; 1.7–2 mm thick; not overgrown; not angular; asymmetrical; reniform, or ovate; compressed; with surface smooth; with visible radicle and cotyledon lobes, or without visible radicle and cotyledon lobes; without external groove between 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, or dull; not modified by a bloom; colored; monochrome, or mottled and streaked; with frequent mottles; with frequent streaks; brown (reddish), or black; with black overlay; glabrous; smooth; coriaceous. Pleurogram absent. Pseudopleurogram absent. Fracture lines absent. Rim absent. Wing(s) absent. Raphe visible; from hilum through lens to base of seed and terminating; not bifurcating; color of testa, or lighter than testa; brown (reddish); flush. Hilum present; visible, or fully concealed; concealed by funiculus; with faboid split; with the lips of the faboid split the same color as the rest of the hilum; larger than punctiform; 0.5–0.8 mm long; with curved outline; circular; marginal according to radicle tip; recessed; within halo; halo lighter than testa. Lens discernible; 0.7–0.8 mm long; with margins curved; circular, or elliptic; not in groove of raphe; adjacent to hilum; 0.8 mm from hilum; mounded; similar color as testa; darker than testa; brown (reddish); not within corona, halo, or rim. Endosperm present; thin; not pluglike and not resembling tip of radicle; covering entire embryo; adnate to testa, or embryo. 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; split over radicle; with lobes; without basal groin formed by lobes; with the interface division terminating at base of radicle; without margins recessed; tan; 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; bulbose; lobe tip straight; deflexed and parallel to cotyledon length; centered between cotyledons; less than 1/2 length of cotyledons. Plumule rudimentary, or moderately developed; glabrous.

Distribution

United States and Mexico.

New World; United States to Mexico.

Generic Notes

Isely and Peabody (1984) and Lavin and Sousa (1995) recognized only four species, the count we used, not the Polhill and Sousa (1981) number of 10(-20) species with this caveat: "Perhaps only four or five basic species.".

Tribal Notes

Tribe Robinieae

The genera, generic groups, and related data follow the tribal treatment of Lavin and Sousa (1995; Polhill, 1994a, 1994b), not Polhill and Sousa (1981).