Abstract: The genus Rhododendron possesses about 850 species ,so it is one of the important componenet of the flora of the North Temperate Zone.In recent era, its center of the distribution lies in Western Szechuan,Northwestern Yunnan,Southeastern Tibet,and though Upper Burma to Eastern Himalaya westwards.In this regions,it possesses not only abundant species and various groups (i.e.Sections and Subsections),but alse the most primitive groups.Basing on these facts,a conclusion could be obtained that the Szechuan-Yunnan Old-land with its adequate surroundings during the geological period ,may be the cradle of the genus.The disjunctive distribution at present of the genus Rhododendron in Europe,Asia and North America probably indicates the close relationship to its center of distribution.

Key words: Rhododendron L.