SUMMARYThe problem of the origin of the genusMangiferahas been discussed in the present paper, with evidence from a thorough analysis of the phytogeographical data and phylogenetic taxonomy of the component species, and also from the climatology (past and present) and geological history of the areas concerned. The phylogenetic taxonomy is based on an exhaustive analysis of the morphological data, with corroborative evidence from cytological, anatomical and pollen morphology studies on the species of the genus, accumulated in the Asiatic herbaria.The phylogenetic taxonomy indicates that the two groups of species under Sections I and II have differentiated early either from a common ancestor or from some of the present species (e.g.M. duperreanaorM. cochinchinensis).The species under Section I have undergone further differentiation into mainly three groups: (1) the pentamerous, (2) the tetramerous and (3) the intermediate having both penta‐ and tetramerous flowers. It appears likely that the second and third groups have evolved from the first group through reduction of floral parts. The stamens have undergone gradual reduction, and series of stages from the presence of five fully developed stamens to those with one developed stamen and complete absence of staminodes are found in the flowers of the various species.The genus had its origin somewhere in the Eastern Peninsula (comprising Burma‐Siam‐Indo‐China and Malaya), during the Eocene or an earlier period in the Cretaceous. The species have then spread to India and Ceylon in the west, and to Eastern Malaysia and the Philippines through the Sunda Archipelago. The two main centres of species differentiation are the Assam‐Burma‐Siam‐Indo‐Chinese region and the Malay Peninsula. Other smaller centres are the Sunda Islands and the Philippines.The most interesting feature of distribution is the paucity of the species (only seven species out of forty‐one) in Eastern Malaysia. Out of the seven species, four belong to Section I and three to Section II. Only one species of Section I is spread over both Eastern and Western Malaysia, but all the three species of Section II are present in both the regions. It, therefore, suggests that the species of Section II had a more primitive origin. They had consequently more time to spread from Western to Eastern Malaysia and to adjust themselves to the Equatorial Monsoon Region of Malaysia. The paucity of the species in Eastern Malaysia is attributable to the unstable archipelagic condition of the region and to the absence of any direct land connexion with the Asiatic mainland since the Cretaceous, when the Angiosperms originated.The actual process of species‐formation is difficult to postulate, but from a cytogenetic analysis of three species of Section I, it is indicated that they had an allopolyploid origin. The numerous varieties ofM. indicaand the two allied species have further differentiated by gene mutations and hybridization. The mode of origin of the species of Section II could not be established as fresh materials for an examination of these species could not be secured from Malaysia during World War II. But the species of Section I, exceptM. duperreana, which are morphologically very much allied, are indicated to have similar mode of origin through hybridization and gene mutations; the distinctive genetic constellation being preserved through isolation. The overlapping and contiguous nature of the areas of distribution of a majority of these species also indicates that hybridization had a major role to play in the process.The range of variation in the genus is limited, and there occur groups of species with almost similar characters. The limited range of variation in the morphological, cytological, pollen and anatomical structures suggests a stabilization of the characters in the species during the earlier epochs since their origin in the early Tertiary. The diversification and evolution that are now taking place among the species are due to gene‐mutations and natural hybridization, which are always occurring in nature. Selection is ultimately playing its role in the sur