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Oenothera mexicana

Distribution: Open sandy soils in southeastern Texas.

Habit: Erect annual herbs, forming rosettes; main stem 15-40 (-60) cm long, up to 1 cm in diameter at base, simple or with arcuating lateral branches arising from the rosette, sometimes flushed with red, moderately to sparsely strigillose and densely long-villous.

Leaves: Leaves alternate, in a rosette and cauline, leaves and bracts grayish green, densely strigillose, rosette leaves 6-10 cm long, 1-2.5 cm wide, narrowly oblanceolate, deeply lobed, the lobes dentate, apex acute, gradually narrowed to the petiole, cauline leaves 3-7.5 cm long, 0.8-2 cm wide, narrowly oblanceolate to oblanceolate, deeply lobed to dentate, apex acute, base narrowly cuneate, sessile to short-petiolate, bracts the uppermost ones erect, 2-4 cm long, 0.7-1.2 cm wide, narrowly oblong or oblanceolate, dentate to subentire, margins revolute, apex acute, sessile.

Flowers: Inflorescence often with lateral branches. Usually one flower per spike opening each day near sunset, floral tube 23-28 mm long, ca. 1 mm in diameter, exclusively glandular-puberulent or scattered to very sparsely villous and sparsely to densely glandular-puberulent, mature buds 34 mm in diameter at the base, oblong to narrowly ovoid or broadly ellipsoid, sepals 5-12 mm long, green, sometimes red-flecked, pubescence like that of floral tube, sepal tips 0.5-2.5 mm long, erect and appressed in bud, strigillose, petals 6-15 mm long, 7-17 mm wide, yellow to pale yellow, very broadly obovate, truncate to slightly retuse, staminal filaments 4-12 mm long, anthers 3-4 mm long, shedding pollen directly on the stigma at anthesis, ovary 8-12 cm long, ca. 1.5 mm in diameter, very densely strigillose, style 27-40 mm long, the exserted part 4-13 mm long, stigma surrounded by the anthers at anthesis, lobes 1-3 mm long.

Fruit: Capsule dehiscent 25-45 mm long, 2.5-3 mm in diameter, cylindrical, densely strigillose, subterete, dehiscent nearly throughout capsule length, sessile.

Seeds: Seeds numerous, in 2 rows per locule, 0.8-1.2 mm long, 0.3-0.5 mm in diameter, ellipsoid to broadly ellipsoid, brown, the surface reticulate and regularly pitted. Seeds numerous, in 2 rows per locule, ellipsoid to subglobose, the surface reticulate regularly pitted.

Chromosomes: Chromosome number: n = 7 (7II* at meiotic metaphase I).

Notes: FNA, Self-compatible and modally autogamous.

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