Oenothera subsect. Gauropsis Torrey & Frémont in J. C. Frémont, Rep. Exped. Rocky Mts., 315. 1845; Gaurella Small; Oenothera subg. Gauropsis (Torrey & Frémont) Munz

Herbs perennial, caulescent; from a taproot, lateral roots producing adventitious shoots. Stems decumbent to ascending, branched. Leaves cauline (basal rosette not observed), (0.3–)0.6–1.5(–2.5) cm; blade margins sinuate-denticulate to subentire. Inflorescences solitary flowers in axils of distal leaves. Flowers opening near sunset, with a sweet scent or nearly unscented; buds erect, terete, without free tips or free tips minute; floral tube (8–)10–15(–17) mm; sepals usually splitting along one suture, remaining coherent and reflexed as a unit at anthesis, rarely separating in pairs; petals usually pink, rarely white, streaked or flecked with red, fading bright purple, obovate; stigma deeply divided into 4 linear lobes. Capsules woody, ovoid, narrowly winged, abruptly constricted to a conspicuous, sterile beak, indehiscent; sessile. Seeds numerous, in 2–4 irregular rows per locule, asymmetrically cuneiform or oblanceoloid and weakly angled (probably resulting from compression from adjacent seeds during development), surface glossy, obscurely reticulate, appearing finely granular. 2n = 14.

Species 1: w United States.

Section Gauropsis consists of one distinctive species with pink petals, flecked with red, and ovoid, indehiscent, narrowly winged capsules and an apex abruptly constricted to a conspicuous sterile beak. It is self-compatible with flowers vespertine, outcrossing, and pollinated by noctuid moths and occasionally hawkmoths, such as Hyles lineata (W. L. Wagner 1984). Wagner indi­cated that O. canescens forms adventitious shoots from lateral roots, but this feature should be re-examined, since the closely related O. speciosa (sect. Hartmannia) reproduces by rhizomes.

One illegitimate later homonym has been published for this taxon: Gauropsis (Torrey & Frémont) Cockerell (1900) not C. Presl (1851).

SELECTED REFERENCE Wagner, W. L. 1984. Reconsideration of Oenothera subg. Gauropsis (Onagraceae). Ann. Missouri Bot. Gard. 71: 1114–1127.