67. Oenothera pallida Lindley, Bot. Reg. 14: plate 1142. 1828.
[F]
Anogra pallida (Lindley) Britton; Oenothera albicaulis Pursh var. pallida (Lindley) H. Léveillé
Herbs annual or perennial, glabrous, strigillose and/or villous, sometimes more villous distally, especially on flower parts; from a taproot, sometimes lateral roots producing adventitious shoots. Stems erect or ascending, single to several from base, unbranched or many-branched throughout, 10–50(–70) cm. Leaves cauline, rosette usually weakly developed or absent, at least during flowering, sometimes well developed, 1–5(–7.8) × 0.3–1(–1.5) cm; petiole 0–2(–4.5) cm; blade lanceolate, oblong, linear-lanceolate, or ovate, margins subentire or remotely denticulate, deeply sinuate-dentate, or pinnatifid, sometimes repand. Flowers 1–several opening per day near sunset; buds nodding, weakly quadrangular, with free tips 0–2 mm; floral tube 15–40 mm; sepals 10–30 mm, not spotted; petals white, fading pink to deep pink, broadly obovate or obcordate, (10–)15–25(–40) mm; filaments 9–15 mm, anthers 3–10 mm; style 25–55 mm, stigma exserted beyond anthers at anthesis. Capsules spreading to reflexed, straight to curved or contorted, cylindrical, obtusely 4-angled, tapering slightly from base to apex, 15–60 × 1.5–2.5 mm; sessile. Seeds numerous, in 1 row per locule, brownish with dark spots or black, narrowly obovoid, 1.5–2.2 mm.
Subspecies 4 (4 in the flora): w, c North America, n Mexico.
Oenothera pallida is a poorly understood species currently subdivided into four subspecies (W. L. Wagner et al. 2007) that differ largely in aspect, leaf division, capsule configuration, and pubescence. The variation pattern is rather complex with almost no diagnostic character uniformly distinguishing any one of the subspecies. Instead, each of the subspecies, which are mostly geographically separated although there is some level of overlap, have diagnostic suites of characters that maintain their linkage some of the time, but break down across the geographic area of each so that no single character uniquely identifies it. Each subspecies is characterized by leaf, pubescence, and, often, habit features. The issues with the integrity and intergradations of the subspecies are discussed below.
Oenothera pallida has been determined to be self-incompatible (W. L. Wagner et al. 2007), but K. E. Theiss et al. (2010) determined that although most populations of subsp. Pallida are self-incompatible, one near Salt Lake City is self-compatible.
