Onagraceae: Evening-primrose Family — Suncups & Primroses
This group includes two genera, Camissonia and Camissoniopsis which used to be treated as one genus but have now been separated. There are three differences between them; Camissonia has more or less straight fruits, cauline leaves only and its flowers are on the uppermost nodes, Camissoniopsis generally has coiled fruits, basal and cauline leaves and its flowers borne on nodes along the whole stem. Individual members of these two families can be extremely hard to distinguish; careful attention must be paid to the types of hairs, presence or absence of glands and the presence or otherwise of small red spots at the base of the petals.
All members of this family have 4-petaled flowers, no more, no less.