Oenothera hartwegii
Oenothera sect. Calylophus
Fendler evening primrose, Hartweg's sundrops
1–many, erect to ascending, unbranched to densely branched, 4–60 cm.
decumbent to ascending or erect, branched or unbranched, epidermis gray to brown, ± exfoliating.
0.3–6.5 × 0.04–1.2 cm, sometimes fascicles of small leaves 0.1–1.5 cm present in non-flowering axils;
petiole 0–0.2 cm;
blade elliptic, lanceolate, linear, or filiform to ovate or oblanceolate, usually not much reduced distally, proximalmost leaves sometimes obovate to spatulate, base attenuate to obtuse, truncate, or subcordate, sometimes clasping, margins entire or serrate, often undulate, apex acute.
cauline, 0.3–9 cm, fascicles of small leaves often present in larger leaf axils;
blade margins entire or subentire, serrate, or serrulate, sometimes spinulose.
solitary flowers in axils of distal leaves.
usually 1 per stem opening per day in afternoon or near sunset;
buds with free tips 0.5–6 mm;
floral tube 16–50(–60) mm, funnelform in distal 1/2 or less;
sepals 7–28 mm;
petals yellow, fading pale pinkish or pale purple, 10–35 mm;
filaments 4–13 mm, anthers 5–13 mm, pollen 85–100% fertile;
style 25–65(–75) mm, stigma yellow, quadrangular, usually exserted beyond anthers.
opening near sunset or sunrise, sometimes in afternoon, usually with a sweet scent;
buds erect, terete or quadrangular, with free tips;
floral tube 2–60(–70) mm;
sepals flat or with keeled midribs, reflexed individually;
petals yellow, usually fading dark yellow, orange, pale pink, or pale purple, suborbiculate to rhombic or obcordate;
stigma usually yellow to yellow-green, blue-black in O. capillifolia subsp. capillifolia, peltate, discoid to quadrangular, sometimes shallowly 4-lobed.
6–40 × 2–4 mm, hard, promptly dehiscent throughout their length.
woody and hard to thin and ± papery, straight, cylindrical to obtusely 4-angled, often tapering at each end, dehiscent 1/2 to throughout their length;
sessile.
obovoid, 1–2.5 mm.
usually numerous, in 2 rows per locule, usually obovoid and somewhat angled, rarely oblanceoloid, surface smooth.
= 14, 28.
= 14 (28).
Oenothera hartwegii
Oenothera sect. Calylophus
Subspecies 5 (5 in the flora).
Oenothera hartwegii consists of five intergrading subspecies, which are generally locally common on rocky, sandy, gypsum, or limestone soil in arid to relatively mesic open areas, in southeastern Colorado, southwestern Kansas, western Oklahoma, Texas (except eastern part), New Mexico, southeastern and east-central Arizona, and in Mexico from Chihuahua, northern Coahuila, and northwestern Tamaulipas south to Aguascalientes. H. F. Towner (1977) found that O. hartwegii is self-incompatible and usually vespertine; two of the subspecies (filifolia and maccartii) open early in the afternoon and are pollinated both day and evening.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Species 7 (7 in the flora).
Section Calylophus consists of 7 species (13 taxa) classified in two subsections distributed throughout the Great Plains to Arizona and south to central Mexico with a center of diversity in Texas (H. F. Towner 1977). P. H. Raven (1964) separated Calylophus from Oenothera as treated by P. A. Munz (1965) based on its peltate stigma and unusual sporogenous tissue (Towner). The peltate stigma can now be more properly interpreted as a variation from the typical Oenothera stigma, with the indusium enlarged and the lobes reduced (W. L. Wagner et al. 2007). Molecular studies (R. A. Levin et al. 2004) strongly support both the inclusion of Calylophus within Oenothera and the monophyly of the section by inclusion of a species from each of the subsections. Subsequent detailed analyses (B. Cooper, unpubl.) indicate that subsect. Salpingia is not monophyletic with subsect. Calylophus nested within it, indicating that subsections may not be justifiable as currently defined. All species, except O. serrulata, are self-incompatible and outcrossing; flowers diurnal to vespertine, opening in the early morning or from midafternoon to near sunset, wilting in one and one-half to two days; those species with diurnal flowers are pollinated by bees [especially Halictidae (halictids) and Anthophoridae (anthophorids), often oligolectic species], those with larger vespertine flowers are pollinated by hawkmoths (Towner). The self-compatible O. serrulata is autogamous and a PTH species. Recent work (M. Moore, pers. comm.) suggests that there is additional edaphic endemism within sect. Calylophus, which is being investigated using morphology and molecular analyses (B. Cooper, unpubl.), and will likely result in detection of previously unknown species in the section.
Meriolix Rafinesque ex Endlicher 1840 is a superfluous name that pertains here.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaves (except proximalmost): blade base truncate or subcordate and clasping; plants densely pubescent with mixture of hair types, but always short-pilose and usually also hirtellous, sometimes also strigillose, especially on leaves, or glandular puberulent distally. | subsp. pubescens |
1. Leaves: blade base attenuate or obtuse; plants glabrous, sparsely strigillose, or glandular puberulent. | → 2 |
2. Plants usually glabrous throughout, sometimes glandular puberulent on distal parts, especially on ovary. | subsp. fendleri |
2. Plants strigillose and/or glandular puberulent, especially on distal parts. | → 3 |
3. Plants glandular puberulent throughout, more densely so on distal parts, sometimes also sparsely strigillose on ovary and leaves; leaf blades filiform to narrowly lanceolate. | subsp. filifolia |
3. Plants usually strigillose, rarely glandular puberulent; leaf blade narrowly lanceolate to oblanceolate, sometimes linear. | → 4 |
4. Leaf blades narrowly lanceolate, sometimes linear, margins entire or shallowly and sparsely serrulate, sometimes undulate; plants sparsely to densely strigillose throughout. | subsp. hartwegii |
4. Leaf blades usually narrowly lanceolate to lanceolate or oblanceolate, rarely linear, margins subentire or serrulate, usually crinkled-undulate; plants usually sparsely strigillose, sometimes glandular puberulent. | subsp. maccartii |
1. Sepals with conspicuously keeled midribs; stamens in 2 unequal series, antisepalous filaments 2 times as long as antipetalous filaments 17b. | O. subsect. Calylophus |
1. Sepals without keeled midribs; stamens in subequal series 17b. | O. subsect. Salpingia |
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