Has 226 Figures including 16 color plates covering 143 species. In addition there are an undetermined number of subspecies and many forms described and pictured.
Many very obscure species, some known only in cultivation are pictured and described. Some have not been found insitu, but are species that were originally discovered in cultivation in small villages in Mexico.
An historic, scientific study that documents a fascintating and intriguing genus of the crassulacae, unique to regions North of the equator in the Americas.