Abstract: The spurge family Euphorbiaceae Juss. is a large family of flowering plants, most are herbs, but some, especially in the tropics, are also shrubs or trees, succulent and resemble cacti. Diagnostic values of the leaf chlorophyll of seven members of two genera (Euphorbia L. and Jatropha L.) of Euphorbiaceae Juss. were studied namely E. neriifolia, E. heterophylla, E. convolvuloides, E. hirta, J. curcas, J. gossypifolia and J. multifida. Analysis of variance was used to test for significance differences among the seven taxa considered. There is correlation between the chlorophyll content and leaf area; the plant (E. heterophylla) with larger leaf area (203.49cm2) has highest chlorophyll content (8.63g/cm2) and J. curcashas the lowest mean leaf area (64.41cm2) lowest chlorophyll content of 1.28g/cm2. Such correlation was not observed between the leaf per gram fresh weight and chlorophyll contentand % chlorophyll content, where E. convolvuloides has the higher leaf area per gram fresh weight (162.79g) and E. heterophylla has the least (89.85g). Generally, species of Euphorbia have higher features in % chlorophyll content (E. heterophylla-75.07%), chlorophyll content (E. heterophylla-8.63g/cm2), leaf area per gram fresh weight (E. convolvuloides-162.79g) and leaf area (E. heterophylla-203.49) than the Jatropha species. These features are found to be good taxonomic characters and thus indented dichotomous taxonomic keyswere constructed based separately for the two genera.