Oenothera sect. Leucocoryne

Herbs annual or perennial, caulescent; from a slender taproot, [sometimes lateral roots pro­ducing adventitious shoots]. Stems several(–many), decumbent to ascending, usually branched. Leaves in a basal rosette and cauline, cauline 1.8–7 cm; blade margins weakly serrulate to subentire, sinuate-pinnatifid, or coarsely sinuate-dentate. Inflorescences solitary flowers in axils of distal leaves. Flowers opening near sunset, scent unknown or unscented; buds erect, terete, with free tips; floral tube 5–30 mm; sepals usually splitting along one suture, remaining co­herent and reflexed as a unit at anthesis, rarely separating in pairs; petals white, fading lavender to pink [or deep purple], obovate to obcordate; stigma deeply divided into 4 linear lobes. Capsules hard and leathery, straight, clavate or obovoid, winged, wings 0.5–4 mm, apex rounded, obtuse or bluntly acuminate, proximal part a sterile pedicel-like base (stipe), gradually tapering to base, valve midrib raised, dehiscent at apex or nearly throughout body; sessile. Seeds numerous, clustered in each locule, narrowly obovoid, surface glossy, appearing granular, but minutely papillose under magnification. 2n = 14.

Distribution

Texas, Mexico, West Indies, Central America, South America, introduced in Europe, Asia, s Africa, Pacific Islands (Hawaii), Australia.

Discussion

Species 5 (2 in the flora).

Section Leucocoryne consists of five species that occur from southern Texas, through north­ern Mexico to the Trans-Volcanic Belt of central Mexico, southward to Guatemala, Nicaragua, and Costa Rica, in openings in pine-oak or conifer forests on slopes or along streams (or arroyos), sometimes along roadsides or other weedy habitats, at 1400–2800(–3250) m elevation.

Species of section Leucocoryne share white petals, have similar capsule shape with a rounded to bluntly acuminate apex, and buds with free tips. All but Oenothera dissecta A. Gray ex S. Watson were formerly included in a more broadly defined sect. Hartmannia. Oenothera dissecta, previously included in sect. Gauropsis (P. A. Munz 1965; W. L. Wagner 1984), was transferred to sect. Leucocoryne, because it has capsules most similar to those of other white-flowered species grouped here (Wagner et al. 2007). All sect. Leucocoryne species are self-compatible (unknown in O. luciae-julianiae W. L. Wagner), the flowers vespertine, pollinated by hawkmoths or autogamous (O. kunthiana and presumably O. luciae-julianiae). Oenothera kunthiana is a PTH species and forms a ring of 14 chromosomes in meiosis; O. luciae-julianiae also appears to be a PTH species, indicated by lowered pollen fertility (Wagner 2004). Section Leucocoryne species are diploid (n = 7), except O. dissecta, which is known exclusively as a tetraploid (n = 14); the chromosomes of O. luciae-julianiae have not been examined.

Oenothera dissecta and O. luciae-julianiae both occur in Mexico. Oenothera dissecta occurs in flats in Durango, Jalisco, San Luis Potosí, and Zacatecas; O. luciae-julianiae occurs in pine-oak forest habitats in the Sierra Madre Occidental from Chihuahua south through Durango, Guanajuato, Nayarit, Jalisco, Michoacán, and Querétaro.

Selected References

None.

Lower Taxa

Oenothera kunthiana, Oenothera tetraptera

Key

1	Petals 20–43 mm; pollen 85–100% fertile; stigmas exserted beyond anthers at anthesis; floral tubes 10–30 mm.	Oenothera tetraptera
1	Petals 8–25 mm; pollen 35–65% fertile; stigmas surrounded by anthers at anthesis; floral tubes 5–31 mm.	Oenothera kunthiana