Mimosa ligustrina Jacquin, Fragm. Bot., 2(?): 29, t. 32, fig. 6. 1801. — . . circa Caracas [Venezuela] crescit." — No typus seen, but the description and figure definitive. — Inga ligustrina (Jacquin) Willdenow, Sp. Pl. 4:1007. 1806. — Pithecolobium ligustrinum (Jacquin) Klotzsch ex Bentham, Trans. Linn. Soc. London 30: 571. 1875, homonym, poster., non P. ligustrinum (Vahl) Bentham, 1844. Bentham included as a doubtful synonym of P. macrostachyum the Mimosa ligustrina Jacquin, which has 6 year’s priority over the basionym M. macrostachys Vahl (Eclog. Amer. 3: 34, t. XXCI. 1807 = Pithecellobium hymenaeifolium (Willd.) Bentham) and might appear to invalidate the combination. Bentham’s note of interrogation following Inga ligustrina (Jacq.) Willd. (Int. Code Bot. Nom. Art. 52, Note 1. 1994) legitimizes the combination P. macrostachyum.

Pusaetha scandens (Linnaeus) var. acutifolia O. Kuntze, Revis. Gen. Pl. 1: 204. 1891. — "Venezuela: Puerto Ca- bello." — Holotypus, NY (hb. Kuntze.)!.

Pithecolobium insigne M. Micheli ex J. D. Smith, Bot. Gaz. (Crawfordsville) 20: 285. 1895. — "San Pedro Sula, Depart. S. Bárbara, Honduras, alt 600 ft., Apr. 1890, C. Thieme, no. 5208." — Holotypus, US 942409V, isotypus, NY!. — Provisionally equated with P. lanceolatum by Zamora, 1991: 134.

Pithecollobium calostachys Standley, Contr. U.S. Natl. Herb. 20: 190. 1919. — ".. . collected in the vicinity of Tampico, Tamaulipas, Mexico, altitude about 15 meters, April, 1910, by Edward Palmer (no. 307)." — Holotypus, US 463247!, isotypus, NY! = NY Neg. 10368. — Provisionally equated with P. lanceolatum by Zamora, 1991: 134.

Pithecollobium pachypus Pittier, Contr. U.S. Natl. Herb. 20: 457. 1922. — "... collected in the vicinity of San Salvador, El Salvador, in 1905, by Carlos Renson (no. 218)." — Holotypus, US 399510!, isotypus, NY! = NY Neg. 10364. Pithecollobium spinulosum Pittier, Contr. U.S. Natl. Herb. 20: 459. 1922. — ".. . collected in the Lands of Loba, Department of Bolívar, Colombia, April or May, 1916, by H. M. Curran (no. 169)." — Holotypus, US 970123!, isotypus, NY!.

Pithecellobium velutinum Britton & Rose, N. Amer. Fl. 23: 19. 1928. — "Near Labradas, Sinaloa [Mexico], September 18, 1925, Roxana S. Ferris & Ynes Mexia 5084T — Holotypus, DS 145678 in CAS!; clastotypus + photo, NY!; isotypus, US 1265907!.

Pithecellobium albicaule Britton & Rose, N. Amer. Fl. 23: 19. 1928. — "Panuro [= Pánuco], Veracruz, April, 1888, [Ed.] Seler 690, type'' — Holotypus, US!; clastotypus + photo, NY! = NY Neg. 1-369.

Pithecolobium campechense Lundell, Phytologia 1: 481. 1941. — "MEXICO: Campeche, Palizada, July 25-28, 1939, Eizi Matuda 3866." — Holotypus, MICH n.v.; isotypus, NY!.Pithecellobium [variously spelled] lanceolatum sensu Standley, 1922: 393; Pittier, 1927: 33 [where type said to be from "Barcelona (Anzoátegui)"]; Standley & Steyermark, 1946: 76 (exclus. syn. P. macrosiphon et winzerlingii)', Woodson & Schery, 1950: 238 (iisdem exclu.); McVaugh, 1987: 234; Zamora, 1991: 134.

Pithecellobium calostachys sensu Standley, 1922: 393; Fl. Yucatan 280. 1930.

Pithecellobium ligustrinum sensu Pittier, 1927: 33; Steyermark, Fl. Avila 561. 1978.

Arborescent shrubs and trees potentially 9-16 (-20) m tall with trunk sometimes attaining 6 dm diam (commonly smaller), but often flowering when 1.5-3 m and in marginal habitats no taller, randomly armed with spinescent stipules (but many specimens seemingly unarmed), the annotinous branchlets densely pallid-lenticellate, the young growth together with most lf-axes and all inflorescence-axes densely or thinly puberulent or pilosulous with fine, spreading or subappressed, pallid hairs 0.1-0.45(-0.55) mm, the chartaceous lfts olivaceous, a little paler beneath, usually glabrous or glabrous except for a tuft of hairs dorsally in anterior basal angle of midrib, occasionally ciliolate, or puberulent on one or both faces, the mostly solitary, either dense or looser and elongating spikes of whitish, white-stamened, fragrant fls laterally and terminally pseudoracemose-paniculate, each peduncle (or pair of peduncles) subtended by a rudimentary bladeless lf-stk bearing a nectary, the whole inflorescence exserted from foliage or some early peduncles axillary to fully expanded lvs. Stipules of many flowering branchlets firm but not spinescent, erect, subulate or compressed-conic ±0.5—2 mm, those of some or all long-shoots widely spreading- ascending, longer, and vulnerant, some attaining 15 mm. Lf-formula i/1, the lfts exactly 4 per lf, but lvs quite variable in dimensions according to habitat and position on the plant, the early lvs of vigorous long- shoots largest, the distal ones often either abruptly or gradually reduced in size; nectary at tip of lf-stks sessile, shallow-patelliform or cupular, round or crumpled, thin- or thick-rimmed, 0.7-1.6(-2.3) mm diam, and a similar nectary at tip of each pinna- rachis; lf-stks of most lvs l-4.5(-5) cm, but shorter in some distal lvs, all shallowly concave ventrally but only a little widened upward; pinna-rachises 4-19 (-22) mm, distinctly dilated distally; lft-pulvini 1.4— 2.5 x 1-1.6 mm, coarsely cross-wrinkled; lfts inequilaterally elliptic or ovate-elliptic from broadly cuneate or semicordate base, obtuse or emarginate, sometimes obscurely bluntly acuminate, the larger ones 3.5-9.5(-14) x (1.2-)l.6-4(-4.5) cm, 1.7-2.8(-3.3) times as long as wide; venation pinnate, the subcentric and gently incurved or straight and diagonal midrib giving rise on each side to 6-11 (-12) major and random intercalary secondary nerves, brochido-drome well within the plane margin, and these in turn to an irregular open reticulum of veinlets, the whole venation finely prominulous on both faces of blade and often pallidly discolored. Peduncle and rachis of spikes together 4—15 (-17) cm, the fls subhorizontal, often a little accrescent upward along the spike and some smaller ones functionally staminate; bracts ovate- or deltate-apiculate to linear-lanceolate, 0.3-2.5(-2.8) mm, persistent; perianth 5-merous or randomly 3-6-merous, externally strigulose or silky- pilosulous overall, the corolla often a little more densely so than calyx; calyx campanulate, sometimes deeply so and sometimes a little constricted below the teeth, (0.8-)l-3.8 x 0.8-1.5(—1.9) mm, the tube nerveless or externally 5-, sometimes 10-nerved, the triangular or depressed-deltate teeth 0.15-0.45 mm; corolla 4-6.5 mm, the ovate lobes erect, often of unequal length, to (0.6-) 1-2.2 mm; androecium (28-) 32-58(-60)-merous, (9-)10-19(-23) mm, the tube  4.5-11(—13) mm, either tubular or distally expanded and trumpet-shaped, either as long as corolla or exserted to 5(-6) mm, the stemonozone ±1 mm; disc 0; ovary sessile or almost so, ellipsoid or oblong- ellipsoid, either glabrous or laterally puberulent; ovules 8-10. Pod solitary or to 4 per spike, erratically ascending, narrowly subcylindroid but more or less biconvex and as ovules abort erratically pinched between seeds, outwardly falcate or sometimes recurved through a full circle, or irregularly sinuous or convolute, measured along the valves (3.5-) 5-12 (-15) cm and at the seeds most often 0.7-1.2 cm, but in SE Mexico to 2.5(-2.7) cm, 7-12 mm diam, the thickly fleshy, reddish, when ripe lignescent and fuscous valves either glabrous or glabrate, rugulose lengthwise or irregularly papillate or both, the stiffly papery endocarp fawn-stramineous but reddish in the seed-cavities, tending to separate from mesocarp after dehiscence; dehiscence elastic, either follicular (through the ventral suture only) or through both sutures, the valves either simply gaping or randomly recurved and coiling; seeds pendulous on and almost fully invested by the elaborately frilled funicular aril, plumply ellipsoid ±10-15 x 7.5-10 mm, the bony planoconvex cotyledons enclosed in a thinly papery and fragile, smooth or wrinkled, brown or dark brown testa lacking pleurogram.

In deciduous and semideciduous brush-woodland, surviving disturbance, and in sunny places, especially along streams, in submontane forest, ascending from the coast, where sometimes impinging on mangrove, to 300 m, but in Nueva Galicia to 800 m and along the Río Cauca in Colombia to 1100 m, locally plentiful: in South America from state of Sucre in Venezuela W along the Caribbean slope to Santa Marta, Colombia, and on the N slope of the Orinoco basin to Maracaibo basin, thence S up the Magdalena and Cauca valleys to about 2°30'N; in Central America and Mexico scattered, mostly below 300 m, from Darién in Panama to the Pacific and Gulf slopes of Mexico as far as 23- 24°N. — Map 9. — Fl. in most months of the year, when not drought-inhibited, new fls sometimes coinciding with ripe fruit. —Ahoga-gato, conchi, ñaure, piquiqua, taquapire, timuche, tucuy (Mexico); abracade (El Salvador); bianco, buche, buche bianco, pinta mono, tiracó (Colombia); laguadrí, maíz cocida, oroce, yacure (Venezuela).

Pithecellobium lanceolatum is a handsome small tree, easily known by the combination of amply quadrifoliolate leaves and paniculate spikes of fragrant white flowers. In foliage it resembles P. roseum but this differs at anthesis by capitulate flowers and red or bright pink filaments, and in fruit by a relatively thin-textured fruit and hard areolate seeds. The more closely related P. hymenaeifolium, similar in lignescent fruit and thin-coated exareolate seed, has denser spikes of larger flowers, much longer and further exserted androecial tube, and a characteristic cristate and velutinous epicarp of the ripe pod.

From a South American viewpoint, P. lanceolatum is taxonomically straightforward, the variation in pubescence of leaves and ovary and in length of corolla and androecium being insignificant in the context of the genus. So far as is known, the barren branches are always armed, but the flowering branchlets are often only feebly so, or spineless. In Central America and lowland Mexico the variation in flower size, in proportionate lengths of calyx to corolla and of corolla to androecium, and in absolute length of the androecial tube becomes accentuated, and to some extent is related to geographic dispersal. As a general rule the androecial tube is a little longer and a little further exserted on the Gulf lowlands in Mexico than on the Pacific slope, where the inflorescence remains nearly uniform from Sinaloa southward into Colombia. The accumulation of herbarium specimens now shows that variation in indumentum of leaves, in length of spikes and number of flowers, in length of floral bracts, in depth of calyx, and in length of perianth are all continuous, independent, and geographically random. Variation in the fruit provides a still unsolved problem, which requres extensive field observation. Two fruit forms, so far as known not correlated with any floral feature of substance, have been recognized at the specific level. In typical P. lanceolatum the mature pod is slender in proportion to its length, commonly about 9-12 mm diameter at each one of about 5-9 seeds; its valves, though unyieldingly lignescent at maturity, are relatively thin-walled and commonly dehisce through the length of both sutures. By contrast the so-called P. pachypus, which is the fruiting counterpart of flowering P. calostachys, has a massively woody pod that swells to as much as ±2.5 cm diameter at the seeds, and that often, but not consistently, dehisces only along one suture or only through the upper part of both sutures; moreover, its seeds gain in volume as space is provided by a larger cavity. Often but not quite always this broad pod is also shorter and fewer-seeded than that of typical P. lanceolatum, as though incomplete fertilization of the ovary had diverted a fund of resources from several to fewer ovules, with consequences not only for the individual seeds but for the bulk of the fruit itself. However, we still lack firm correlation between a broad  fruit and any particular flower type and are unable to predict the fruit type from antecedent flowers. The pachypus-type fruit is apparently dominant in Veracruz, northern Oaxaca, Chiapas, and Petén, but is replaced by a slender one in parts of Yucatán Peninsula. It has not been detected on the Pacific slope in Mexico, nor in South America, and may yet deserve infraspecific taxonomic status.

Pithecellobium lanceolatum and the three species following (Pp. johansenii, winzerlingii, and hymenaei- folium), may be recognized at anthesis by exactly quadrifoliolate leaves accompanied by spiciform units of inflorescence. The spikes vary in length and density, but when relatively short and therefore comparable to those exceptional spicate populations of P. unguis-cati, the androecium is longer (at least 16 mm, usually more). At maturity of the fruit, the papery exareolate seed-coat combined with the simply grooved (not green-winged) leaf-stalks and the number of leaflets per leaf separates these four species from all other species, whether quadrifoliolate or not. Due to this syndrome of characters we were inclined to separate these four species in a section distinct from the remainder of Pithecellobium. The phylogenetic analysis shows, however, that doing so would result in the rest of Pithecellobium being paraphyletic.

The definition of P. lanceolatum and the same three species following is hindered by (a) uniformity in aspect of the foliage such as to make sterile material unidentifiable; (b) marked plasticity in size and form of those few features of inflorescence and fruits that are taxonomically promising or have been thought to be so; and (c) difficulty in matching fruits and flowers, which are seldom encountered on the same individual tree. The center of variability for the group is in southeastern Mexico and neighboring Central America, and its taxonomy in this region is far from securely settled. The two species that occur in South America are separable there by linked characters of the flower and fruit: relatively short androecium and narrow glabrate, variably roughened but not cristate fruit of P. lanceolatum contrast sharply with the extremely long androecium and bluntly undulate-cristate, minutely velutinous fruit of P. hymenaeifolium. The same two taxa become less clearly differentiated in western Central America, where discontinuities between lengths of androecium and contrasts between types of pericarp in the fruit are much less precise and are weakened by sometimes sympatric P. winzerlingii, which has relatively short androecium coinciding with cristate pods. Absolute and proportional lengths of the calyx, corolla, and androecium are extraordinarily (and independently) labile, to some degree even within a single unit of inflorescence. In general, the calyx of P. lanceolatum is campanulate and less than 2 mm deep, two or three times shorter than the corolla, but is randomly modified into a cup as much as 5 mm deep that almost (R. Torres 4619, CAS) encloses the corolla. This floral modification, like the indumentum of foliage and the length of floral bracts, occurs independently of other macromorphologic variation and independently of dispersal. However, the poorly known P. johansenii may be an exception to this rule. Comment on the heteromorphic fruits of P. lanceolatum will be found under that species.

The flowers of P. lanceolatum, P. johansenii, P. winzerlingii, and P. hymenaeifolium are vespertine, white, and fragrant; they have a long narrow androecial tube, and they seem ideally suited to pollination by night-flying long-tongued Lepidoptera. It is theoretically possible that the exaggerated length of the androecial tube in P. hymenaeifolium has been mediated by selection, perhaps more than once, from different stocks of P. lanceolatum, but we do not know whether this modification has been accompanied by intersterility other than differentiation of the pollinator, as has occurred in the Orchidaceae.