Pterodon

Taxonomy

Pterodon J.R.T. Vogel Linnaea 11: 384. Apr-Jul 1837.

Subfamily: Faboideae.
Phylogenetic Number: 3.3.03.
Tribe: Dipteryxeae.
Species Studied - Species in Genus: 3 studied; ca. 6 in genus.

Description

Fruit: A nutletnutlet:
small, hard, indehiscent, one-seeded fruit
, or a legumelegume:
usually dry, dehiscent fruit derived from a single carpel that opens along two longitudinal sutures
; unilocular; 3–6 cm long; 2–3.5 cm wide; 0.5–0.7 cm thick; length less than twice as long as width; with deciduous androecial sheath; with deciduous corolla; with deciduous calyx; without orifice formed by curving of fruit or fruit segments; straight; not plicate; not twisted; symmetrical; oblong to ovate; inflated; flattened; without beak; tapered at apex, or rounded at apex; aligned with longitudinal axis of fruit; short tapered at base to rounded at base; aligned with longitudinal axis of fruit; with the apex and base uniform in texture; drupaceous; seed chambers externally invisible; margin not constricted; margin without sulcus; margin plain, or embellished; margin with wing(s); wing(s) present (readily visible when epicarp exfoliates); wing(s) 1; wing(s) 5–25 mm wide (most of our samples with damaged or nearly missing wings); wing(s) continuous wing around fruit; substipitate; indehiscent. Replum invisible. Epicarp dull; monochrome; black; with surface texture uniform; glabrous; without spines; not smooth; not veined; not tuberculate; exfoliating; with cracks; cracking irregular; without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp present; thick; surface veined over seed chamber and inconspicuously veined on wing; 1-layered; with balsamic vesicles; without fibers; without reniform canals; firm-walled open empty cells (with balsamic vesicles); ligneous. Endocarp present; visible; dull; opaque; monochrome; tan; fibrous, or spongy; without adhering pieces of testa; nonseptate; coriaceous; not exfoliating; remaining fused to mesocarp and epicarp; with wing(s) extending into epicarp (readily visible when epicarp exfoliates); entire. Seed(s) 1; length parallel with fruit length. Funiculus 0.5–1 mm long; thick; straight. Aril present; dry; when dry rim-aril; entire; brown.

Seed: 8.5–9.5 mm long; 4–5 mm wide; 1.5–3.5 mm thick; overgrown, 1 seed filling entire fruit cavity; not angular; symmetrical (except for hilum); oblong, or ovate; compressed; 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; not modified by a bloom; colored; monochrome; black, or tan; glabrous; smooth; coriaceous. Pleurogram absent. Pseudopleurogram absent. Fracture lines absent. Rim absent. Raphe visible; from hilum through lens to base of seed and terminating; not bifurcating; darker than testa; black; flush. Hilum present; partially concealed to fully concealed; concealed by aril; with faboid split; with the lips of the faboid split the same color as the rest of the hilum; punctiform; marginal according to radicle tip; recessed; within rim; rim color of testa. Lens discernible; 1 mm long; with margins straight, or curved; oblong; oblong; not in groove of raphe; adjacent to hilum; mounded; dissimilar color from testa; darker than testa; dark brown; within rim; rim color of testa. Endosperm absent. Cotyledons smooth; both outer faces convex; both the same thickness; both more or less of equal length; not folded; margin entire 180 degrees from base of radicle; similar at apex; partially concealing radicle; split over radicle; with lobes; with the interface division terminating at base of radicle; white; 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; straight with embryonic axis; centered between cotyledons; less than 1/2 length of cotyledons. Plumule well developed; glabrous.

Distribution

Brazil and Bolivia.

New World; South America (Brazil and Bolivia); Brazil.

Generic Notes

Polhill (1981c) noted that a "critical reappraisal is needed" for Pterodon. Hutchinson (1964) noted that the seeds are "full of balsam oil." The mature epicarp readily exfoliates leaving the mesocarp with its fragile wing and woody seed chamber. Other legumelegume:
usually dry, dehiscent fruit derived from a single carpel that opens along two longitudinal sutures
fruits whose winged mesocarps "dehisce" from the epicarp include these diverse genera: Amburana (3.1.15), a faboid genus in tribe Sophoreae; Schizolobium (1.17), a caesalpinioid genus in tribe Caesalpinieae (Gunn, 1991); and, Wallaceodendron (5.16), a mimosoid genus in tribe Ingeae (Gunn, 1984). The former two genera have winged mesocarps that are samaralike, and the latter genus has winged mesocarp segments that have two marginal wings. Pterodon has a wing that encirles the mesocarp unit.

Tribal Notes

Tribe Dipteryxeae

Polhill (1981c) noted that the tribe has "woody dehiscent valves, or with stony endocarp tardily opening on ground, or winged around the hard central seed-chamber with epicarp flaking.".