This theory, if true, would change significantly our present understanding of California biogeography. Oddly enough, few, if any, biologists have hurried to embrace it. The taxonomy of Dudleya has been especially turbulent. The species were first classified in the South African genus Cotyledon , then they were transferred briefly to Echeveria . Finally they came to rest in the eponymous genus named after Stanford professor William Dudley.
Many species vary considerably, and others intergrade maddeningly.
The expert on the genus, who wrote the monograph of Dudleya in the 1950s, has said that he is sick of the whole thing. Whatever their names, there are many beautiful species. D. candida is native to Cedros Island. It is similar to D. virens , but has its leaves coated with a dense farina. D. traskiae has glaucous, flat leaves and pale yellow flowers.