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Oenothera centauriifolia

Distribution: Occurring in small scattered populations in damp areas along arroyos, streams, fallow fields and roadsides from Argentina in the east part of the provinces of Santa Fe and Choco, east to the provinces of Corrientes and Entre Rios, in Uruguay from the departments of Salto, Paysandu, Durazno, Soriano, Colonia, Canelones and Montevideo; also from single scattered localities from Argentina in the provinces of Tucuman, Santiago del Estero and Cordoba and from Brazil in the state of Rio Grande do Sul, sea level to ca. 500 m.

Habit: Caulescent perennial herb from a stout taproot usually producing adventitious shoots from slender lateral roots, the stems green or sometimes tinged with reddish purple, (15-)20-50 cm long, erect, becoming ascending in age, densely to sparsely short-villous and glandular pubescent, appearing glabrous.

Leaves: Leaves bright green, thin, major lateral veins prominent, short-villous and glandular pubescent usually more densely so along the margins and veins, narrowly oblanceolate to oblanceolate, (6-)9-15(-25) cm long, 2-4(-6) cm wide, irregularly and very coarsely pinnately lobed, usually with a large terminal lanceolate to ovate lobe, the margin of which is coarsely serrate or dentate, apex of lobes acute, tapering to a petiole (0.6-)1-3(-4) cm long.

Flowers: Buds with unequal free tips (2-)3-6.5 mm long, flowers 1-2 per stem per day, produced only along the stem, opening near sunset. Ovary moderately to densely glandular pubescent and short-villous, 14-18 mm long, sessile, floral tube (9-)11-15(-19) cm long, 1-2 mm in diameter medially, flaring to 5-8 mm at the mouth, sparsely to moderately glandular pubescent and short-villous, sepals green, (2.7-)3-4.5 cm long, 3-5 mm wide, pubescence the same as on the floral tube, petals white, fading whitish to pale lavender, drying pale lavender, obovate with a small terminal tooth to obcordate, 3-5(-5.3) cm long, 3-5(-5.5) cm wide. Staminal filaments white, 17-24 mm long, anthers pale yellow, 9-15 mm long, style whitish, 15-19(-23) cm long, stigma lobes 5-10 mm long, well elevated above the anthers.

Fruit: Capsule narrowly obovoid to clavate, (15-)20-30(-32) mm long, 9-12 mm in diameter, becoming hard and woody in age, the surface conspicuously wrinkled, constricted to a short beak, the free tips spreading or sometimes erect, 1-3 mm long, the valves with a triangular wing 3-5(-7) mm wide, confined to the upper 1/2 of the capsule, abruptly truncated and absent or nearly so from the lower half, dehiscing 1/4-1/3 the length of the capsule.

Seeds: Seeds ca. 140-190 per capsule in two adjacent and distinct rows, asymmetrically cuneiform, usually curved and somewhat adaxially concave, brown to dark purplish brown often mottled with lighter areas, 2.5-3.3 mm long, 1.5-2.1 mm wide, 0.6-0.8 mm high, the surface minutely beaded, broadly winged at the distal end, the wing often erose, continued narrowly along one adaxial margin, the raphe slightly raised.

Chromosomes: Gametic chromosome number, n=7.

Notes: Flowering from September to March. Self-compatible and apparently outcrossing, but selfing when flowers fade.


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