was left intact. Thus two subgenera, Hymenanthes and Azaleastrum were expanded at the expense of four subgenera that were eliminated, although Azaleastrum lost one section (Choniastrum) as a new subgenus, since it was a distinct subclade in A. In all, Hymenanthes increased from one to two sections, while Azaleastrum, by losing one section and gaining two increased from two to three sections. (See schemata under Subgenera) (Table 1.) Subsequent research has supported the revision by Goetsch, although has largely concentrated on further defining the phylogeny within the subdivisions. In 2011 the two species of Diplarche were also added to Rhododendron, incertae sedis. Subdivision This genus has been progressively subdivided into a hierarchy of subgenus, section, subsection, and species. Subgenera Terminology from the Sleumer (1949) system is frequently found in older literature, with five subgenera and is as follows; Subgenus Lepidorrhodium Koehne: Lepidotes. 3 sections Subgenus Eurhododendron Maxim.: Elipidotes. Subgenus Pseudanthodendron Sleumer: Deciduous azaleas. 3 sections Subgenus Anthodendron Rehder & Wilson: Evergreen azaleas. 3 sections Subgenus Azaleastrum Planch.: 4 sections In the later traditional classification, attributed to Chamberlain (1996), and as used by horticulturalists and the American Rhododendron Society, Rhododendron has eight subgenera based on morphology, namely the presence of scales (lepidote), deciduousness of leaves, and the floral and vegetative branching patterns, after Sleumer (1980). These consist of four large and four small subgenera. The first two subgenera (Rhododendron and Hymenanthes) represent the species commonly considered as 'Rhododendrons'. The next two smaller subgenera (Pentanthera and Tsutsusi) represent the 'Azaleas'. The remaining four subgenera contain very few species. The largest of these is subgenus Rhododendron, containing nearly half of all known species and all of the lepidote species. Subgenus Rhododendron : Small leaf or lepidotes (scales on the underside of the leaves). 3 sections, 462 species, type species: Rhododendron ferrugineum. Subgenus Hymenanthes : Large leaf or elepidotes (without scales). 1 section, 224 species, type Rhododendron degronianum. Subgenus Pentanthera : Deciduous azaleas. 4 sections, 23 species, type Rhododendron luteum. Subgenus Tsutsusi : Evergreen azaleas. 2 sections, 80 species, type Rhododendron indicum. Subgenus Azaleastrum : 2 sections, 16 species, type Rhododendron ovatum. Subgenus Candidastrum : 1 species, Rhododendron albiflorum. Subgenus Mumeazalea : 1 species, Rhododendron semibarbatum. Subgenus Therorhodion : 2 species (Rhododendron camtschaticum, Rhododendron redowskianun). For a comparison of the Sleumer and Chamberlain systems, see Goetsch et al. (2005) Table 1. This division was based on a number of what were thought to be