Oenothera subsect. Salpingia
Syst. Bot. Monogr. 83: 148. 2007.
Herbs perennial, sometimes suffrutescent, or annual.Leaves: blade margins entire, serrulate, or serrate. Flowers usually 1 to several per stem opening per day in afternoon or near sunset or sunrise; buds terete; floral tube 5–60(–70) mm; sepals flat, midrib not keeled; stamens in 2 subequal series, pollen 85–100% fertile. Capsules hard or papery, straight or slightly curved, promptly dehiscent 1/2 to throughout their length. Seeds obovoid, rounded or sharply angled. 2n = 14 (28).
w United States, Mexico.
Species 4 (4 in the flora).
Subsection Salpingia consists of four species (nine taxa) ranging from eastern Nevada and Utah to western Nebraska and adjacent Wyoming, south in Mexico to Chihuahua, northeastern Sonora, Nuevo León, southwestern Tamaulipas, and San Luis Potosí, at elevations 30–2600 m. Flowers of subsect. Salpingia are diurnal or vespertine (and opening in afternoon or evening). Salpingia (Torrey & A. Gray) Raimann (1893), not Salpinga Martius ex de Candolle (1828), is a later homonym and pertains here.
|1||Floral tubes 5–25(–33) mm, funnelform in distal 1/2 or more; flowers diurnal, opening near sunrise.||Oenothera tubicula|
|1||Floral tubes (15–)16–60(–70) mm, funnelform in distal 1/2 or less; flowers vespertine opening in afternoon or near sunset.||> 2|
|2||Leaf axils with conspicuous fascicles of small leaves, these 0.2–2.5 cm; flower buds with free tips 2–9(–12) mm; capsules somewhat papery and dehiscent in distal 1/2.||Oenothera toumeyi|
|2||Leaf axils sometimes without axillary fascicles of leaves, when present, these 0.1–1.5 cm; flower buds with free tips 0.3–6 mm; capsules hard, dehiscent throughout.||> 3|
|3||Plants not cespitose, stems erect to ascending, 4–60 cm, strigillose, glandular puberulent, glabrous, hirtellous or short-pilose.||Oenothera hartwegii|
|3||Plants low, often cespitose, stems spreading to decumbent or ascending, 4–20(–30) cm, densely strigillose throughout, sometimes glandular puberulent distally.||Oenothera lavandulifolia|