Oenothera L.

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1981, Flora Europaea. Volume 2. Rosaceae to Umbelliferae, Cambridge University Press : 306

3. Oenothera L. 1

( Onagra Miller ) Annual, biennial or perennial herbs. Leaves alternate. Flowers actinomorphic, rather large, in a leafy spike; hypanthial tube conspicuous. Sepals 4, deflexed in flower; petals 4, yellow or rarely pink; stamens 8, in 2 whorls; stigma deeply 4-lobed; ovary 4-locular. Fruit an elongate, loculicidal capsule; seeds small, numerous, without a chalazal plume of hairs. Plants of American origin cultivated for ornament in Europe and widely naturalized, usually on disturbed ground. Several other species, not described here, have been recorded as casuals. Literature: O. Renner, Ber. Deutsch. Bot. Ges. 60: 448-466 (1942); 63: 129-138 (1950); Planta 47: 219-254 (1956). K. Rostahski, Fragm. FI. Geobot. 11: 499-523 (1965). 1 Petals pink to reddish-violet; flowers opening near sunrise

13. rosea 1 Petals yellow, often becoming reddish or purplish; flowers opening near sunset

2 Cauline leaves oblong-ovate or broadly oblanceolate, ± truncate at base; plant densely hispid 10. longiflora 2 Cauline leaves lanceolate or elliptical, cuneate at base; plant not densely hispid

3 Hypanthial tube 70-100 mm 11. aflinis 3 Hypanthial tube 15-50 mm

4 Capsule conspicuously enlarged distally; seeds pendent, not sharply angled 12. stricta 4 Capsule not enlarged distally; seeds horizontal, sharply angled

5 Sepal-apices divergent in bud; inflorescence ± nodding at anthesis 7-9. parviflora group 5 Sepal-apices appressed to one another in bud; inflorescence erect 1-6. biennis group