Started by: AGS EncyclopaediaGo to latest contribution by Jim McGregor, 30 January 2013, 11:45. Go to bottom of this page.
I note in the entry for the above that although the text states that there are 6 species only 5 are actually listed.
No mention is made of R. baurii which is the most commonly grown. Mention should also possibly be made that R. baurii has 3 varieties - R. baurii var. baurii, R. baurii var. platypetala, and R. baurii var confecta.