A detailed cytological investigation of the endosperm in Datura fastuosa Linn. has revealed that the endosperm is basically triploid (3n=36) eventhough it becomes mixoploid by the appearance of higher ploid cells and some aneuploid cells in course of development. Endopolyploidy is brought about by endoreduplication, dispersion endomitosis, C-mitosis like division and also nuclear fusions. This is correlated with the vigorous growth of the endosperm and the fruit in general and hence may be considered as a positive adaptation.