A genus of two semi-herbaceous shrubs, both Californian, one extending into Mexico. The leading characters of the genus are the pinnately divided leaves, the large white usually solitary flowers with four to six petals and three soon deciduous sepals, numerous stamens, sessile stigmas connate at the base, capsular appressed bristly fruits splitting by valves and containing numerous small seeds.
The generic name commemorates the Irish astromoner Dr F. Romney Robinson, a friend of Dr Coulter, who discovered the type-species (for further information on the history of the generic name see Bot. Mag., n.s., t. 678).