Pithecolobium corymbosum Bentham, London J. Bot. 3: 221. 1844. — "British Guiana, [Richard & Robert] Schomburgk, n. 114 of 1841 [2nd. coll.]; Cayenne, Martin; Surinam, Hostmann, n. 214, 262, and 1190; Borba on the Rio Negro [really lower Río Madeira, Riedel, commun.] Langsdorff." — Lectotypus, Schomburgk 114 of 1841, K!; paratypi, Riedel [no. 67], Martin s.n., Hostmann 214, 1190, all K!. — Samanea corymbosa (Bentham) Pittier, Bol. Ci. Técn. Mus. Com. Venez. 1: 55. 1926, without full citation. —Equated with the preceding by Bentham, 1875: 587; 1876: 440, with reservation; Kleinhoonte, 1940: 327 (all excluding syn. Steudel).

Pithecolobium subcorymbosum Hoehne, Comiss. Linhas Telegr. Estratég, Mato Grosso Amazonas, Bot. 8: 18, est. 133. 1919. — "Hoehne Nos.: 4582-4586 ... em S. Luiz de Caceres, nas margens do rio Paraguay, perto da Campina [in SW Mato Grosso, Brazil, near 16°S, 57°40'W]. [16°S, 57°40'W] — Syntypi, SP, not seen, but the illustrated protologue unambiguous.

Pithecolobium corymbosum var. longipes Spruce ex Ducke, Bol. Técn. Inst. Agron. N. 18: 37. 1949, nom. nud. [Spruce 2429 e Panuré ad Rio Uaupés, K!, NY!].

Broad-crowned riparian trees attaining 5-20 m with trunk 1-3 dm dbh, the annotinous epidermis cracking vertically and exfoliating, the young ones and all lf-axes (at least ventrally) and peduncles pilosulous with incurved, gray or sordid hairs up to 0.1-0.25 mm, the amply microphyllidious lvs bicolored, the lfts on upper face dark olivaceous brunnescent (overall, or in spots, rarely remaining green), either lustrous venulose or dull and nearly veinless, on lower face dull, pale olivaceous or pale tan and almost always minutely, often remotely strigulose, the umbelliform capitula consisting of many small crowded, slenderly pedicellate, whitish or reddish peripheral fls surmounted by a sometimes elongate pedestal bearing 1-4(-7) much longer and sessile or subsessile, white or white and basally pink sterile fls with modified androecium, the peduncles either 1-3 (-4) together and axillary to fully developed lvs, or the upper ones, sometimes nearly all, axillary to hysteranthous lvs, the inflorescence then becoming terminally pseudoracemose and sometimes shortly exserted (but the terminal meristem potentially continuous). Stipules linear or linear-lanceolate 2—7(—8.5) x 0.3-0.7 mm, caducous with early expansion of associated lf, absent from mature spms. Lf-formula ii—v(—vii)/(4—)5—11(—14); lf-stk of most developed lvs 4-14(-18) cm, but that of depauperate lvs of some lateral flowering branchlets only 0.8-3.5 cm, the petiole (0.7-)1-4(-5) cm, at middle ±1-2 mm diam, the one or the longest interpetiolar segment (0.7-)1-3.5(-4.2) cm, the shallow ventral groove of each narrowly dilated upward; petiolar nectaries sessile or shortly stoutly stipitate, in vertical view round or obtusangulately scutiform ±1-2.5 mm diam, either mounded and dimpled, or almost plane, or cupular and coarsely marginate, the first one nearly always at or close below first pair of pinnae (exceptionally wanting) and similar ones between all, some, or no further pairs, and smaller, distinctly stipitate, cupular or trumpet-shaped nectaries on pinna-rachises between 2-7 distal pairs of lfts; pinnae usually sub-accrescent distally, the rachis of distal or penultimate pair (3-)3.5-9.5(-11) cm, the interfoliolar segments dilated upward, the longer ones 5—13(—15) mm; minute paraphyllidia close above most pinna-pulvini; lft- pulvinules cross-wrinkled 0.5-1.2 x 0.6-0.9(-1) mm; lfts accrescent upward from base of rachis or subequiform (except for broader farthest pair) upward from midrachis, in outline broadly or narrowly rhombic-oblong from inequilateral, postically rounded, antically cuneate base, obtusangulate and at apex broadly obtuse or faintly emarginate, those near and above midrachis (11-) 12-31 (-35) x (4)4.5-14 mm, (1.7-)2- 3.3(-4.5) times as long as wide; venation pinnate, the slender, straight or weakly incurved, subcentric or subdiagonal midrib giving rise to 7—12(—13) major and indefinite intercalary secondary nerves brochidodrome well within the plane margin and to an open sinuous reticulum, the whole venation most commonly finely prominulous on both faces, sometimes only beneath. Peduncles (1.5—)3—11 (—13) cm, in fruit ascending stout and lignescent, long persistent; capitula (30-)35-75-fld, at full anthesis subhemispherical, the fls strongly dimorphic, the pedicellate peripheral ones crowded on a narrowly clavate receptacle 2.5-5.5 mm, the pedestal of the 1-4(-5) furthest sessile or subsessile fls drum-shaped ±1 mm diam to linear and to 5-8 mm; bracts dimorphic, those of peripheral fls linear or linear-oblanceolate 0.7-2 mm, those of (sub)terminal ones linear-elliptic 2-4.5 mm, all early dry caducous; PERIPHERAL FLS: pedicel of lower ones (4—)5—11.5(—13) x 0.1-0.2 mm; perianth 5(-6)- merous, usually finely minutely strigulose overall,  but sometimes only the calyx-teeth and corolla-lobes puberulent, or the whole perianth glabrous except for ciliolate corolla-lobes; calyx campanulate or turbinate-campanulate (1—)1.4—2.6 x 0.6-1.2(-1.4) mm, the ovate-triangular, often unequal teeth 0.3-0.7 mm; corolla (2.6-)3.5-6(-6.5) mm, the lobes (1—)1.2—2.3 x 0.7-1.2 mm; androecium 10—18(—22, in occasional fls transitional to the terminal ones, -32)- merous, (11-) 13-24 mm, the stemonozone 0.4-0.9 mm, the tube 1.3—2.6(—3) mm, the filaments white or greenish white; ovary a trifle dilated and truncate at apex, puberulent around the top or over the distal half, otherwise glabrous; style as long as or a trifle longer than longer filaments, at apex poriform or slightly dilated, less than 0.2 mm diam at the stigma; TERMINAL FL(S): pedicel 0 or to 1 mm, nearly as thick; calyx either broadly campanulate or cylindro-campanulate 3-6 x (0.8-)1.3-2.2 mm; corolla (6.5-)7.5-11.5(—15) mm; androecium 24-34-merous, the stemonozone 2-4 mm, the indurated tube 7-11 mm, ±1 mm shorter to 3 mm longer than corolla, the free part of the biseriate filaments more or less thickened and tortuous. Pods 1-7(-8) per capitulum, erect, either sessile or contracted at base into a pseudostipe 1-5 mm, in profile broad-linear (4.5-)5-10.5 x (0.9-)1-1.7(—1.9) cm, broadly rounded and apiculate at apex, straight or nearly so (sometimes bent sideways, but not decurved), the valves at first piano-compressed, brown-fuscous and often somewhat lustrous, minutely puberulent especially toward the base, becoming coriaceous or lignescent, dull brown or purplish black and often distally glabrate, low-convex over seeds and depressed between them, transversely venulose, the mature fruit lomentiform, the valves readily cracking between seeds and more reluctantly through the dorsally plane, shallowly undulate sutures (0.8-1.6 mm wide), the 1-seeded articles transversely oblong, as wide as the pod and (5-)5.5-9(-10) mm long, along the line of fracture 0.9-2 mm thick; seeds transverse, snugly fitting the cavity of each segment, basifixed on a filiform crumpled funicle, compressed but plump, in broad view 7.3-9.8 x 4-5.3(-5.6) mm, the firm crustaceous, tan or brown testa closely investing the hard greenish embryo, the complete, narrowly oblong pleurogram ±6—7.5 x 1.6—2.5 mm.

In periodically or permanently inundated riparian forest and (southward) in gallery forest, mostly below 200 m but attaining 480 m in Venezuelan Guayana, widespread through lowlands of the Orinoco and Amazon basins, in Venezuela from Apure and Guárico E to Delta-Amacuro and nearly throughout Venezuelan Guayana, thence W to the llanos of Arauca in NE Colombia and S in Brazil to Acre, adjacent Pando in Bolivia, and the Madre de Dios valley in SE Peru, to Rondonia, Mato Grosso, and N Goiás, in Mato Grosso extending into the Paraguay basin S to the Pantanal; from Brazil W through extreme SE Colombia to the upper Napo in Ecuador and the middle Ucayali valley in Peru; the three Guianas; and in Brazil E to Maranhão. — Map 2. — Fl. most prolifically V-IX, randomly in other months. — Arepito, bizcochuelo, hueso de pescado rebalsero (Venezuela); paschaca, paschaca blanca (Peru); swamp manariballi (Guyana); bois macaque, préfontaine blanc, tamalin (French Guiana); angico branco, pau bixeiro, saboeira da varzea (Amazonian Brazil); tipa macho (Bolivia).

Hydrochorea corymbosa varies in leaf-formula, flower-size, shape of terminal flowers, and width of fruit, but no pattern of correlation has been found among these or between any one of them and dispersal. Leaves on vigorous new long-shoots have relatively many and large leaflets, whereas leaves of short lateral branchlets, as exemplified by the typus of Pithecellobium subcorymbosum, tend to be shorter and fewer. The peripheral flowers of a capitulum in this species may be uniform or slightly accrescent distally, occasionally becoming transitional to the terminal flower in a combination of slender pedicel and duplex androecium. The modified terminal flowers may be exactly one per capitulum or two to three, when one it is either sessile or carried up beyond adjacent peripheral flowers on a stalklike pedestal. The calyx in the first case is campanulate, in the second more deeply campanulate or tubular. Collectors who have noted the color of flowers agree that the filaments are whitish and the corolla greenish white or pink-tinged. The flowers of Prance 23591 (NY, from Río Urubú, Amazonas, Brazil) are described as dark red, but this may refer only to the corolla. Normally the perianth is gray-puberulent, conspicuously gray-tipped in bud, but a form with glabrous calyx and almost glabrous corolla has been encountered on upper Río Branco in Brazil and in neighboring Guyana (cf. Black 51-13300, Maas 6362\ both NY).