On the Classification and Distribution of the Subfamily Populoideae(Salicaceae)

The subfamily Populoideae(Salicaceae) naturally distributes in tropical Africa and in the Northern Hemisphere from about 19°to 70°north latitude,and consists of two genera,i.e.Balsamiflua and Populus.The genus Balsamiflua,with two sections,i.e.sect.Balsamiflua et sect.Abaso and about 3 natural species,disjunctively disperses in equatorial Africa,Tethyan region and Mexico.The genus Populus contains two subgenera,i.e.subgen.Leucoides(incl.sect.Leucoides) et subgen.Populus(incl.sect.Tacamahaca,sect.Aigeiros et sect.Populus) and about 52 natural species,and widely ranges in Europe,Asia,North America et the northern fringe of Africa.A key to the genera of Populoideae,a key to the sections et species of Balsamiflua,a key to the subgenera et sections of Populus and the keys to the species of each section in Populus are drafted.A checklist of the poplar species is provided,including their correct names,synonyms,bibliographic references,geographic distributions etc.