Monographs Details: Pithecellobium furcatum Benth.
Authors:Rupert C. Barneby
Authority: Barneby, Rupert C. & Grimes, James W. 1997. Silk tree, guanacaste, monkey's earring: A generic system for the synandrous Mimosaceae of the Americas. Part II. , , and . Mem. New York Bot. Gard. 74: 1-149.
Family:Mimosaceae
Discussion:17. Pithecellobium furcatum  Bentham, London J. Bot. 5: 106 (sub Pithecolobio). 1846. — "On the Rio Teapa in [Tabasco] South Mexico, Linden." — Holotypus, Linden 723, collected VIII-IX, 1838 (fl.), K! = K Neg. 15527 = photo s.n., NY!; isotypus, F!.

Pithecolobium furcatum sensu Bentham, 1875: 581 (misplaced in sect. Auaremotemo); Standley, 1922: 394. Pithecelobium (?) furcatum sensu Britton & Rose, 1928: 23.

Macrophyllidious trees and arborescent shrubs 3-12m with trunk to ±1 dm dbh, randomly armed at nodes with stout, widely ascending, straight tapering stipular spines, appearing glabrous to the gray-silky corollas but the young branchlets and units of inflorescence somewhat thinly minutely pallid-puberulent, the ample, truly glabrous, dull olivaceous lfts subconcolorous, the short, often capituliform spikes of white vespertine fls either axillary to coeval lvs or forming a short efoliate peudoraceme. Stipules at armed nodes 4-12 mm, at base dilated and recurrent, those at unarmed nodes stiffly subulate-acicular ±0.5-2 mm, all persistent. Lf-formula i/1, each lf 4- foliolate; lf-stks 0.6-5.5 cm, usually broadly mar- ginate, the herbaceous wings wider upward and to 10 mm distally, but the wings occasionally lacking or almost so; a sessile cupular nectary ±0.6-1 mm diam at tip of lf-stk and at tip of each pinna; pinna-rachises 6-15 mm, like the lf-stk marginate or not; lfts elliptic or obovate-elliptic from inequilateral, either cuneate or shallowly semicordate base, shortly bluntly acuminate, the larger ones 3.5-9.5 x 1.5-3.5 cm, 2.3-3.3 times as long as wide; venation pinnate, the subcentric midrib gently incurved, giving rise to ±7-10 pairs of major and indefinite intercalary secondary nerves brochidodrome shortly within the plane margin, and these in turn to an open reticulum of veinlets, the whole venation finely prominulous on both faces or subimmersed on upper one. Peduncles solitary 0.4-3 cm; spikes ±14—35-fld, the axis 4-12 mm, the homomorphic fls ascending, the perianth 5-merous, the calyx firm brown striate, thinly strigulose, the corolla externally silky with appressed gray hairs; bracts ovate- or deltate-acuminulate 0.7-1.5 mm, persistent; calyx cylindric or cylindro-campanulate 4.5-7.5 x ±2 mm, the often unequal, ovate apiculate teeth 0.6-1.5 mm; corolla narrowly trumpet-shaped 8-12 mm, the ascending ovate lobes 1.7-2.5 x 1.2-2 mm; androecium 36-62-merous, 31-46 mm, the stemonozone 1.6-2.2 mm, the slender tube 11-30 mm; disc 0; ovary minutely stipitate, the ellipsoid body densely puberulent; style shortly exserted from stamens, the stigma poriform. Pods (few seen) sessile, in profile oblong, gently recurved, ±5x2 cm, laterally compressed but plump, the fuscous-castaneous woody valves becoming finely rugulose, early glabrescent; dehiscence follicular, through the ventral sutures; funicle tapelike, dilated into a scalloped aril nearly half as long as seed, this not seen fully mature.

In riparian forest below 100 m, localized in SE Mexico (S Veracruz, E Oaxaca, Tabasco, N Chiapas), adj. Guatemala (Alta Verapaz), and Belize (Toledo). The white flowers (Sousa 9216, CAS) begin to expand at 4:00 P.M. — Not mapped. — Fl. II, VI, IX, X, XII, the full season unknown. — Amezquite.

Pithecellobium furcatum is unique in the greenwinged leaf-axes that recall species of Inga and Swartzia arborescens, even though these, of course, have once-, not twice-, pinnate leaves.