At www.flora.sanbi.org one sees that there are 1700 mesemb or Aizoaceae species worldwide, grouped into 127 genera. To complicate matters, there are today about 6000 mesemb species names around in the literature! These include many synonyms and old, discarded names that still persist all over the botanical and popular literature. No wonder the confusion arising from identification discussions!
Fortunately there is an official system in place, serviced by an international authority of which South African botanists form an organized part. The interested amateur may, with some effort come to understand the binomial naming system and the taxonomic structure started by Linnaeus in the 18th century. More daunting are the current conventions for updating names and groupings, every time the authorities decide to recognise new knowledge.