Sleumer's system underwent many revisions by others, predominantly the Edinburgh group in their continuing Royal Botanic Garden Edinburgh notes. Cullen of the Edinburgh group, placing more emphasis on the lepidote characteristics of the leaves, united all of the lepidote species into subgenus "Rhododendron", including four of Sleumer's subgenera ("Rhododendron", "Pseudoazalea", "Pseudorhodorastrum", "Rhodorastrum"). In 1986 Philipson & Philipson raised two sections of subgenus "Aleastrum" ("Mumeazalea", "Candidastrum") to subgenera, while reducing genus "Therorhodion" to a subgenus of "Rhododendron". In 1987 Spethmann, adding phytochemical features proposed a system with fifteen subgenera grouped into three 'chorus' subgenera.