Pithecellobium

Taxonomy

Pithecellobium C.F.P. von Martius Nom. cons. Flora 20(2) (Beibl. 8): 114 ('Pithecollobium'). 21 Oct 1837.

Subfamily: Mimosoideae.
Phylogenetic Number: 2.5.11.
Tribe: Ingeae.
Species Studied - Species in Genus: 8 studied; 18 in genus.

Description

Fruit: A legume; unilocular; (3.5–)5–25(–27) cm long (Barneby and Grimes, 1997Barneby and Grimes, 1997:
Barneby RC and Grimes JW. 1997. Silk tree, Guanacaste, Monkey's Earring: A generic system for the synandrous Mimosaceae of the Americas. Part II. Pithecellobium, Cojoba, and Zygia. Mem. New York Bot. Gard. 74(2): 1&-161. ); 0.5–2.5(–2.7) cm wide (Barneby and Grimes, 1997); 0.3–1.2 cm thick (Barneby and Grimes, 1997); 2–9 times longer than wide, or more than 9 times longer than wide; with deciduous androecial sheath; with deciduous corolla; with deciduous calyx; with orifice formed by curving of fruit or fruit segments, or without orifice formed by curving of fruit or fruit segments; curved to 0.5-coiled to 1-coiled to 1.5-coiled to 2-coiled to 3-coiled to 4-coiled to 5- to 10-coiled; not plicate; not twisted, or twisted (sometimes); symmetrical, or asymmetrical; oblong to linear, or C-shaped, or falcate (rarely); with both sutures parallelly curved; not inflated; terete to compressed; without beak; short tapered at apex to rounded at apex, or abruptly long acuminate at apex; aligned with longitudinal axis of fruit; tapered at base to short tapered at base; aligned with longitudinal axis of fruit; with the apex and base uniform in texture; ligneous, or leathery; seed chambers externally visible to invisible; seed chambers with the raised seed chambers not torulose; margin not constricted to constricted; margin constricted along both margins, or constricted on 1 margin and slightly constricted on the other margin (dorsal margin slightly constricted); margin without sulcus; margin plain; wing(s) absent; stipitate, or substipitate; with the stipe up to 12 mm long (and thick); with all layers dehiscing; splitting along suture(s). Dehiscence of valves along 1 suture (along ventral margin and reflexing, sects. Virga and Harvardiopsis), or both sutures (not reflexing, sect. Pithecellobium); apical and down; active; with valves when not reflexing, perhaps revolute and twisting (remaining attached to sutures). Replum invisible. Epicarp dull to glossy; monochrome; dark brown to reddish brown, or black, or red, or green; with surface texture uniform; glabrous to glabrate to pubescent and indurate; with hairs erect, or appressed; with 1 type of pubescence; puberulent, or strigose; with pubescence uniformly distributed; with simple hairs (straight or antrorse); pliable; with hair bases plain; eglandular; without spines; not smooth, or smooth; with elevated features; veined; reticulately veined; not tuberculate; rugose; not exfoliating; without cracks; without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp absent, or present; thick, or thin; surface not veined; 1-layered, or 2-layered, or 3-layered; without balsamic vesicles; without fibers; without reniform canals; fibrous throughout, or fleshy, or solid; with solid layer over 2 distinct solid layers; ligneous, or coriaceous. Endocarp present; visible; dull; opaque; monochrome; reddish brown to red, or tan, or orange; smooth, or cracked (longitudinally during reflexing); without adhering pieces of testa; subseptate, or nonseptate; with septa thicker than paper, firm; with septa eglandular; chartaceous, or coriaceous, or ligneous; not exfoliating; remaining fused to mesocarp and epicarp, or separating from mesocarp (rarely); remaining fused to epicarp, or separating from epicarp (rarely); without wings; entire. Seed(s) 2–14; length parallel with fruit length; overlapping (impinging on shape of adjacent seeds), or neither overlapping nor touching; in 1 series. Funiculus 3–12 mm long; of 1 length only; thick (often fringed with arillate tissue, red, pink, or white); slightly curved to straight. Aril present; dry; when dry caplike; entire; covering less than 1/2 of seed, or 1/2 to nearly all of seed (1/3 to 3/4 of seed covered by aril); without tongue (or flap) on lips of 2-lipped rim-aril; reddish brown to black, or white, or red to pink, or orange.

Seed: 4–23 mm long; 3.5–12(–14) mm wide; 4–10(–12) mm thick; not overgrown; angular, or not angular; symmetrical; rectangular to irregular, or elliptic to ovate, or obovate, or pyriform, or reniform, or circular; compressed to terete; with surface smooth; without visible 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; dull, or glossy; not modified by a bloom; colored; monochrome; dark brown to black; glabrous; not smooth, or smooth; with elevated features, or recessed features; rugose to shagreen; pitted with small separate pits, or punctate; osseous to chartaceous. Pleurogram present (sect. Pithecellobium), or absent (sects. Virga and Harvardiopsis); 75–100 %. Pseudopleurogram absent. Fracture lines absent. Rim absent. Wing(s) absent. Raphe not visible. Hilum present; fully concealed; concealed by aril; without faboid split; punctiform to larger than punctiform; 5–10 mm long; with straight outline, or curved outline; circular; linear; apical at apex of radicle tip to subapical to radicle tip; recessed to flush; not within corona, halo, or rim. Lens not discernible, or discernible; 2–5 mm long; with margins straight; linear; not in groove of raphe; recessed; similar color as testa, or dissimilar color from testa; lighter than testa; yellow to tan; not within corona, halo, or rim. Endosperm absent. Cotyledons smooth; both outer faces flat; both the same thickness; both more or less of equal length; not folded, or with only 1 folded (occasionally somewhat); margin entire 180 degrees from base of radicle; similar at apex; completely concealing radicle, or partially concealing radicle; split over radicle; with lobes; with lobes overlapping; with 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 straight; parallel to length of seed; without a joint evident between the radicle and the cotyledons. Radicle differentiated from cotyledon; linear, or triangular; lobe tip straight; straight with embryonic axis; centered between cotyledons; less than 1/2 length of cotyledons. Plumule well developed; glabrous.

Distribution

Central and South America, Mexico, the West Indies, and reaching subtropical Mexico, Bahamas, and peninsular Florida.

New World; Mexico, Central America, South America, West Indies, and United States (peninsular Florida); Peru, Brazil, Ecuador, and the Guianas.

Generic Notes

Pithecellobium species in the sense of Nielsen (1981a) and Barneby and Grimes (1997) have arillate seeds and usually open pleurograms. Only species with arillate seeds were included in our study, and some with a chartaceous testa had no pleurogram (P. lanceolatum). Seeds of P. lanceolatum have a raphe, the point of attachment for the longitudinal aril. Occasionally aril fragments may remain in the fruit, and sometimes the entire aril may be knocked from the seed. Rose (1899) provided a note about the sale in Mexico of P. dulce seeds for the use of their arils as a human food. Oza (1971) studied the seed shapes of P. dulce. Barneby and Grimes (1997) monographed the genus, and their species count and distribution are used. They stated, taht it "differs consistently from all other Ingeae in one character: the seed-funicle modified into a spongy aril that cups the lower one-third or one-half of the seed. At dehiscence the seed is suspended on this red, pink, or white arilliform funicle, which serves as an elaiosome, attractive to birds and edible to man.".