Oenothera sect. Megapterium
Oenothera macrocarpa
bigfruit evening primrose, Missouri evening primrose, Ozark sundrop
ascending or becoming decumbent, usually unbranched.
moderately leafy, (1–)4–40(–60) cm.
in a basal rosette, often also cauline, (2.8–)5–21(–34) cm;
blade margins entire, dentate, or pinnatifid.
cauline, (2.8–)3.7–12.5(–17) × (0.1–)0.4–3(–4.5) cm;
petiole (0.4–)1–4(–6) cm;
blade linear, lanceolate-elliptic, elliptic to oblanceolate or suborbiculate, margins entire or conspicuously or inconspicuously denticulate or serrulate, sometimes undulate, apex usually acute, sometimes obtuse or retuse (subsp. incana).
solitary flowers in axils of distal leaves.
opening near sunset, with sweet scent or nearly unscented;
buds erect, quadrangular, with free tips;
floral tube (21–)35–210(–220) mm;
sepals splitting along one suture, remaining coherent and reflexed as a unit at anthesis;
petals yellow, fading yellow, orange, pink, or deep red, obovate to rhombic-obovate;
stigma deeply divided into 4 linear lobes.
usually 1 or 2, rarely more, opening per day near sunset, fading next morning, sometimes (subspp.
papery, leathery, or corky in age, ovoid, narrowly lanceoloid to broadly ellipsoid, or globose, winged, wings 10–32 mm wide throughout, or capsule walls with corky thickening and wings not developed (sometimes in O. brachycarpa), then capsule appearing only 4-angled, apex truncate to cuneate, dehiscent 1/4–1/3 their length;
pedicellate, sometimes disarticulating from plant at maturity.
papery in age, narrowly ellipsoid to lanceoloid, sometimes twisted (subsp. fremontii), winged, wings (2–)10–28(–34) mm wide, body (13–)25–70(–115) × 2–9 mm, dehiscent 1/4–1/3 their length;
pedicel 1–12(–25) mm.
numerous, in 1 or 2 rows per locule, grayish to yellowish brown, brown, or dark purplish brown, obovoid or subcuboid, angled or rounded, usually with an erose wing distally, surface coarsely rugose and reticulate, thickened, especially at distal end, this area with an internal cavity adjacent to embryo.
numerous, rarely as few as 8, in 1 row per locule, obovoid, (2–)3–5 × 1–2.3 mm.
and oklahomensis) lasting for 2 days, weakly scented;
buds with unequal free tips 1–11(–15) mm;
floral tube (21–)35–140(–160) mm;
sepals (20–)25–65(–75) mm;
petals bright yellow, fading orange, reddish orange or mostly unchanged, obovate to very broadly obovate, (17–)25–65(–68) mm, usually with terminal notch and/or tooth, margin sometimes erose;
filaments 13–40(–44) mm, anthers 10–24(–25) mm;
style (45–)55–192 mm, stigma usually exserted beyond anthers at anthesis.
= 14, 28, 42, 56.
Oenothera sect. Megapterium
Oenothera macrocarpa
Species 4 (4 in the flora).
Section Megapterium consists of four species (eight taxa); two (Oenothera brachycarpa,O. macrocarpa) are diploid (2n = 14), one (O. coryi) is hexaploid (2n = 42), and one (O. howardii) has tetraploid, hexaploid, and octoploid populations (2n = 28, 42, 56) (W. L. Wagner et al. 2007). The species usually occur on xeric rocky sites of limestone, sandstone, shale, or gypsum, rarely (O. brachycarpa) on volcanic soil, from eastern Nevada, Utah, and eastern Colorado east to the Mississippi River in Missouri, and south through northern Arkansas and Texas, to Coahuila, Durango, and Nuevo León, Mexico; there are only two isolated records (O. macrocarpa subsp. macrocarpa from St. Clair County, Illinois, and Rutherford County, Tennessee) from east of the Mississippi River, at 130–3000 m elevation. All species are self-incompatible and vespertine, the flowers fading the following morning, or sometimes remaining open for a second day in O. macrocarpa, pollinated by hawkmoths including Hyles, Manduca, and Sphinx (see Wagner et al. for summary).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Subspecies 5 (4 in the flora).
Oenotheramacrocarpa is variable and has differentiated extensively in the Great Plains region. Each of the five distinctive subspecies occupies a different geographical and ecological situation. Only subsp. mexicana W. L. Wagner from Coahuila, Mexico, occurs outside of the flora area. In general, the subspecies are sharply distinct and each is characterized by a number of features, including pubescence, leaf features, flower and floral tube size, and size and morphology of the capsules and seeds. The five entities are treated as subspecies primarily because of their complete interfertility and extensive intergradation in any area of marginal contact. Intermediates are known between subsp. macrocarpa and subspp. fremontii and oklahomensis and between subspp. incana and oklahomensis. There is also some evidence that suggests past hybridization between subspp. fremontii and incana although there is no present contact between them. All subspecies are self-incompatible.
Oenothera alata Nuttall (1818) is an illegitimate name based on O. macrocarpa and pertains here.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaves (2.8–)3.7–12.5(–17) cm, blade margins entire or denticulate or serrulate; plants caulescent; stems (1–)4–40(–60) cm. | O. macrocarpa |
1. Leaves (3.1–)5–21(–34) cm, blade margins usually pinnately lobed, sometimes lobed only proximally; plants acaulescent or sometimes caulescent; stems 0–20(–36) cm. | → 2 |
2. Petals pale yellow to yellow, drying lavender to purple, usually broadly rhombic-obovate, rarely obovate, usually appearing crumpled; floral tubes (90–)120–210(–220) mm; leaf blade usually with a large terminal lobe, margins usually irregularly pinnatifid with some of the sinuses extending nearly to midrib, margins usually erose; capsule wings 0–3(–5) mm wide. | O. brachycarpa |
2. Petals lemon-yellow to brilliant yellow, drying purple to reddish brown, rarely lavender, broadly obovate, not crumpled; floral tubes (43–)60–110(–125) mm; leaf blade without a large terminal lobe, margins entire or irregularly pinnately lobed, sinuses usually extending less than 1/2 to midrib, margins not erose; capsule wings (2–)4–7(–11) mm wide. | → 3 |
3. Petals brilliant yellow, (30–)40–60(–73) mm, drying deep reddish purple to reddish brown; flowers with strong, sweet scent; buds with free tips 1–3(–4) mm; leaves (0.5–)1–2(–3) cm wide, blades usually oblanceolate, elliptic to narrowly elliptic, rarely lanceolate. | O. howardii |
3. Petals lemon-yellow, 35–43 mm, drying lavender to purple; flowers with weak scent; buds with free tips 0.7–1.2 mm; leaves (0.2–)0.3–0.5(–0.7) cm wide, blades linear to narrowly lanceolate. | O. coryi |
1. Herbs glabrous. | → 2 |
2. Leaf blades usually very broadly elliptic to suborbiculate, rarely oblanceolate or elliptic, 2–4.3 cm wide, margins usually entire, sometimes inconspicuously denticulate, usually flat, sometimes undulate. | subsp. incana |
2. Leaf blades usually elliptic to lanceolate-elliptic, sometimes linear, (0.3–)0.8–2(–3) cm wide, margins usually conspicuously denticulate to serrulate, rarely subentire, usually undulate. | subsp. oklahomensis |
1. Herbs strigillose. | → 3 |
3. Bud free tips 1–2(–5) mm; petals (17–)25–33(–37) mm; floral tubes (21–)35–65(–80) mm; capsules often twisted, 13–30(–65) mm, wings 2–5(–9) mm wide. | subsp. fremontii |
3. Bud free tips (4–)5–11(–12) mm; petals (25–)31–65(–68) mm; floral tubes (50–)70–140(–160) mm; capsules not twisted, (28–)30–70(–115) mm, wings 10–28(–34) mm wide. | → 4 |
4. Leaves green or younger ones grayish green, moderately strigillose, rarely more densely strigillose, blades often lanceolate-elliptic to broadly elliptic, sometimes linear or lanceolate, 0.4–2.3(–3) cm wide; capsule wings (14–)18–28(–34) mm wide. | subsp. macrocarpa |
4. Leaves gray, densely strigillose, blades very broadly elliptic to suborbiculate, rarely oblanceolate or elliptic, 2–4.3 cm wide; capsule wings 10–15(–24) mm wide. | subsp. incana |
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