Prosopidastrum

Taxonomy

Prosopidastrum A.E. Burkart Darwiniana 13: 436. Dec 1964.

Subfamily: Mimosoideae.
Phylogenetic Number: 2.3.18.
Tribe: Mimoseae.
Group: Prosopis.
Species Studied - Species in Genus: 2 studied; 2 in genus.

Description

Fruit: A legumelegume:
usually dry, dehiscent fruit derived from a single carpel that opens along two longitudinal sutures
; unilocular; 4.5–11.5 cm long; 0.5–1.3 cm wide; 0.3 cm thick; 2–9 times longer than wide; with deciduous androecial sheath; with deciduous corolla; with deciduous calyx; without orifice formed by curving of fruit or fruit segments; curved; not plicate; not twisted; symmetrical; linear to oblong; not inflated; compressed; without beak; tapered at apex to 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; coriaceous; seed chambers externally visible; margin not constricted to constricted (slightly or once fully constricted); margin constricted along both margins; margin without sulcus; margin plain; wing(s) absent; substipitate; indehiscent (either entire and separating from replum or segmented through sutures and falling as 1-seeded suture bearing segments). Replum visible. Epicarp dull; monochrome; reddish brown to brown; with surface texture uniform; glabrous to pubescent and indurate; with hairs erect; with simple hairs; eglandular; without spines; not smooth; with elevated features; veined; reticulately veined, or transversely veined relative to fruit length (sometimes absent); not tuberculate; not exfoliating; without cracks; without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp absent. Endocarp present; visible; dull; opaque; monochrome; tan; cobwebby; without adhering pieces of testa; subseptate; not exfoliating; entire. Seed(s) 3–8; length oblique to fruit length; neither overlapping nor touching; in 1 series. Funiculus 0.5–3 mm long; of 1 length only; filiform; curved to plicate. Aril absent.

Seed: 3–10 mm long; 2–8 mm wide; 1.3–5 mm thick; not overgrown; not angular; symmetrical; ovate to rhombic (-ovate), or irregular; compressed; with surface smooth; without visible radicle and cotyledon lobes; without hilar sinus; without umbo on seed faces, or with umbo on seed faces (in P. globosum); 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; glossy; not modified by a bloom; colored; monochrome; brown; glabrous; smooth; coriaceous. Pleurogram faintly present; 50 %. Pseudopleurogram absent. Fracture lines absent. Rim absent. Wing(s) absent. Raphe not visible. Hilum present; visible; without faboid split; punctiform; apical at apex of radicle tip; flush; not within corona, halo, or rim. Lens discernible; 0.3 mm long; with margins straight; oblong to triangular; not in groove of raphe; flush to recessed; same color as testa to similar color as testa; lighter than testa, or darker than testa (blackish, often with S-curved or curved discolored line extending ca. 1 mm away from hilum along seed margin (perhaps where funiculus touched testa)); shades of brown, or black; not within corona, halo, or rim. Endosperm present; thin (or disk atop cotyledons); not pluglike and not resembling tip of radicle; adnate to testa. Cotyledons smooth; both outer faces flat; 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; with lobes; with lobes overlapping; with basal groin formed by lobes; with the interface division terminating at base of radicle; without margins recessed; 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; straight with embryonic axis; centered between cotyledons; less than 1/2 length of cotyledons. Plumule rudimentary; glabrous.

Distribution

Mexico and Argentina (Patagonia).

New World; Mexico and South America (Argentina Patagonia); Argentina.

Generic Notes

Based on fruit and seed characters, Prosopidastrum is heterogeneous: The Mexican species, P. mexicana, shares only tribal characters with the Patagonian species, P. globosum. Dressler (1956) named Prosopis globosa Gillies var. mexicana Dressler without seeing its fruit. He assumed the fruit was a "loment as in the South American variety," P. globosa var. globosa. When Burkart (1964) established Prosopidastrum, he elevated var. mexicana to a species and described the fruits as "dry, linear, compressed, pericarp subcoriaceous, not at all fleshy, lomentloment:
usually dry fruit derived from a single carpel that breaks transversely into one-seeded fruit segments
, dividing into 1-seeded squarish segments or dehiscing by valves, valves separating from persistent replum. Seeds with copious endosperm." These fruit differences apparently did not concern Burkart. More seeds and fruits should be collected and distributed to herbaria.