Oenothera calcicola
Oenothera sessilis
Texas beeblossom
erect, branched below and just above ground, branched also proximal to inflorescences, (40–)60–250 cm.
ascending, unbranched to few-branched, 30–65 cm.
in a basal rosette and cauline, basal 3–13 × 0.6–2.5 cm, blade spatulate to oblanceolate, cauline (1–)2.5–12 × 0.1–1 cm, blade linear to narrowly oblanceolate, margins slightly to conspicuously sinuate-dentate.
in a basal rosette and cauline, basal 2.5–7 ×0.7–2.3 cm, petiole 1–1.5 cm, blade oblanceolate, margins subentire, undulate;
cauline (3–)6–7(–9) ×(0.3–)0.6–0.8(–1.1) cm, sessile, blade lanceolate to narrowly lanceolate, margins subentire.
slender.
nodding, flowers in axils of distalmost few nodes.
4-merous, zygomorphic, opening near sunset;
floral tube 3–9 mm;
sepals 6–12 mm;
petals white, fading dark pink to red, slightly unequal, elliptic-obovate, 7–11 mm;
stamens presented in lower 1/2 of flower, filaments 3–7 mm, anthers 2.5–5 mm, pollen 90–100% fertile;
style 9.5–19 mm, stigma exserted beyond anthers at anthesis.
opening near sunrise;
buds with free tips 1–2 mm, connivent to spreading;
floral tube 10–15(–20) mm;
sepals 10–18 mm;
petals bright yellow, fading pale pink, 15–25 mm;
filaments 7–9 mm, anthers 5–8 mm, pollen 85–100% fertile;
style 10–12 mm, stigma exserted beyond anthers at anthesis.
lanceoloid to narrowly ovoid, narrowly 4-winged, 7–12 × 1.5–2.5 mm, tapered to a sterile stipe 2–5 mm.
ellipsoid, 4-angled, 8–10 × 3–4 mm, stipe 0–2 mm;
sessile.
(2 or)3 or 4(or 5), light brown or reddish brown, 1.5–2.5 × 0.8–1.3 mm.
1 × 0.5 mm.
= 14.
= 56.
Oenothera calcicola
Oenothera sessilis
Oenothera calcicola occurs at mostly higher elevations and more montane areas than other species of subsect. Stipogaura, from the southern Trans-Pecos and Edwards Plateau regions of Texas southward into northern Mexico. P. H. Raven and D. P. Gregory (1972[1973]) determined O. calcicola to be self-incompatible. It is known to form hybrids with O. suffrutescens.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Oenothera sessilis is relatively rare within its range and has a narrow overall distribution, occurring in Ashley, Phillips, Prairie, and St. Francis counties in Arkansas, Allen, Claiborne, and Tensas parishes in Louisiana, and Galveston County in Texas. Oenothera sessilis appears to be relatively rare and may no longer occur in Texas; it was last collected there in the 1840s by Lindheimer on Galveston Island. It is also rare in Louisiana but has been collected in recent decades. It is currently most common in Arkansas. P. A. Munz (1937, 1965) treated this taxon as O. sessilis, but G. B. Straley (1977) in his revision of sect. Kneiffia placed it as a subspecies of O. pilosella based on a common octoploid (2n = 56) chromosome number, morphology, and field studies. K. N. Krakos et al. (2014), based on new field studies, controlled greenhouse breeding experiments, and phylogenetic data found that this taxon differs morphologically from O. pilosella by having consistently shorter stature and smaller flowers, is self-compatible, and does not form a monophyletic group with O. pilosella in molecular analyses, and is here reinstated as a distinct species.
Oenothera sessilis is in the Center for Plant Conservation’s National Collection of Endangered Plants as O. pilosella subsp. sessilis.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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