Language: Bilingual in English and Polish
This work presents 61 species and permanent hybrids of Oenothera occurring in Europe, and provides a key for their identification. The taxa are arranged alphabetically, and each is characterized with its morphological description, general distribution, occurrence in European countries; and more important synonyms are provided. The most significant morphological characteristics are illustrated according to the same scheme for each taxon.
All the quantitative characteristics given in the key and morphological descriptions refer to plants in the first phase of flowering and fruiting, that is, the period from mid-June to end of July. After this phase plants enter a fruiting phase involving maturation of the ovary and seeds, as well as development of side branches below the main inflorescence/infrutescence. In particularly hot and humid summers this year rosettes can develop into flowering shoots, usually in late August or September; however seeds produced by these late-flowering plants never mature before -winter.