Albiziaobliquifoliolata De Wild., Bull. Jard. Bot. État Bruxelles 7: 253 (1920).

Democratic Republic of the Congo, Congo Belge, Eala, Laurent 1823 (lectotype, designated here: BR [BR0000008916334]!; isolectotype: BR [BR0000008916662]!).

Trees up to 30 m in height and up to 1m DBH, the bark with both small scattered and long transverse linear lenticels, the indumentum consisting of a dense rusty to golden-brown pubescence covering the young twigs, petiole and primary rachis, with more sparse pubescence on peduncles and pinna-rachises except for dense rows of hairs at the margins of the otherwise glabrous canaliculate adaxial side of the pinna rachises, often also the canaliculate primary rachis of the leaf sparsely pubescent to glabrous adaxially. Stipules linear deltoid to falcate, 2–3 mm long, adaxially glabrous except at apex, densely pubescent, caducous. Leaves with (1–)2(–3) pairs of pinnae, petiole pulvinate and slightly flattened at base, (1.5–)2–3.5(–4.5) cm long, with a sessile concave circular to triangular nectary at the apex, c. 0.8–1.5 mm in diameter, rachis usually canaliculate adaxially, (0–)1.5–3(–6) cm long, if the leaf 3-jugate then usually with an inter-pinnal nectary, similar to the petiolar one, in between the middle pair of pinnae, apical nectary usually lacking, pinnae distinctly pulvinate, and usually with minute paraphyllidia at the apex of the pulvini, pinna-rachises canaliculate adaxially, the groove glabrous, c. (3–)4–11(–15) cm long, with short stipitate circular to elliptical cupular or trumpet-shaped nectaries c. (0.2–)0.5–1 mm in diameter. Leaflets in (3–)5–7(–8) pairs per pinna, subsessile on a c. 0.5 mm long pulvinule, widely spaced so that the margins do not overlap, bicolorous, dark green and shiny above, pale dull green beneath, rhomboid and often distinctly curved towards pinna apices, base asymmetrically obtuse or slightly oblique and the apex rounded or shallowly emarginate, sometimes mucronate, (1.4–)2.2–3.5(–4.7) × (0.6–)1.1–1.8(–2.2) cm, except the apical pair that is asymmetrically elliptic with oblique base and emarginate apex, (1.8–)2.7–4.8(–5.5) × (1.0–)1.5–2.5 cm, venation pinnate with (6–)12–16(–18) secondary veins brochidodromous, prominent on both surfaces or prominulous to slightly sunken on upper surface, and reticulate tertiary venation, often prominent on upper surface, obscure beneath, margins and midrib ciliate on both surfaces, lamina glabrous but for a few short scattered appressed hairs. Inflorescences (10–)15–20 flowered umbelliform capitula, on long slender peduncles arising 1–2 from axillary buds of coeval or caducous leaves, held above the foliage, the axillary meristems usually not continuous beyond the peduncles and aborted prior to fruit set, dimorphic with a single enlarged terminal flower and often one dispositioned peripheral flower c. 0.5 cm below the others, on peduncles 4–8(–12) cm long. Bracts linear to spatulate, sometimes bilobed at apex, c. 2–3.5 × 0.5 mm, pubescent with longer hairs at apex. Peripheral flowers on pedicels 2–6 mm long, calyx pentamerous, green to greenish white, c. 3–4 mm long, the deltoid lobes c. 0.5 × 0.5 mm, glabrous, corolla pentamerous, green to greenish white, c. 5–6 mm long, the lobes c. 2–3 × 2 mm, glabrous or with short white hairs around the apices of the lobes, androecium consisting of c. 20–30 stamens, c. 2.1–2.5 cm long, the filaments white to pale green at apex, fused into a tube c. 3 mm long, with dorsifixed pale yellowish green anthers, pollen in 16-celled plano-compressed disc-shaped polyads, pistil c. 2.5–2.8 cm long, ovary c. 3 mm long, pubescent in upper half, the pale green to white style emerging from it at an angle of c. 45°, with a green funnel-shaped stigma, extending beyond the stamens. Terminal flower sessile to subsessile, similar to peripheral flowers but broadly campanulate and larger, calyx c. 3.5–5 mm and corolla c. 7.5–9 mm long, the filaments thicker and staminal tube c. 8–10 mm long, exserted well beyond the corolla tube. Pods falcate and weakly articulated, base often tapering into a c. 5 mm long stipe, (3–)6–12 seeded with a thin papery fruit wall and slightly thickened rim, dark brown to black outside when ripe, light brown inside, (3.7–)5.5–9.6 × 1.2–1.4 cm, breaking up into 1-seeded articles 0.4–0.7(–1.0) cm long, the basal and apical articles up to 1 cm long, seed c. 6.5 × 4.5 × 0.5 mm, the testa hard, light brown with a darker brown closed elliptic pleurogram, c. 4 × 2 mm.

Gabon, Central African Republic, Congo-Brazzaville, Democratic Republic of the Congo. Hydrochoreaobliquifoliolata occurs in the Congo Basin, and is a species of swamp forests, seasonally inundated forests and riverbanks.

The similarities to Cathormionrhombifolium, the other African species that is here transferred to Hydrochorea, are discussed below.

Gabon: Ogooué-Lolo, road Okondja to Bambidie and Lastoursville, 21 km SW of Okondja, 7 February 2008, J.J. Wieringa 6519 (BR, K). Democratic Republic of Congo: Yafunda, rive guache, près d’Isangi, 8 September 1938, J. Louis 11175 (BR). Boendu, August 1938, Du Bois 904 (BR), G. Couteaux 55 (BR). Bolomba, 7 November 1957, C. Évrard 2746 (BR). Bongoy, 4 January 1958, C. Évrard 3191 (BR). Botsima, route station-village, 28 January 1991, J.B.M.M. Dhetchuvi 321 (BR). Yangambi, île Tutuku en face du plateau de l’Isalowe, 3 January 1940, R.G.A. Germain 87 (BR). Bokondji, 28 September 1959, De Wanckel 162 (BR).