The results of hybridization betweenC. lacryma-jobiLinn. var.lacryma-jobiLinn. (2n= 20) andC. giganteaKoenig ex Roxb. (2n= 12) and the phylogenetic affinities between these two species are discussed in this paper. C.lacryma-jobivar.lacryma-jobi(2n= 20) is cosmopolitan and the most widely distributed species of this genus, whileC. gigantea(2n= 12) occurs as isolated populations in the paddy fields in certain regions of South India. Both species are clearly distinguishable by their morphological features. The karyotype of both species differ very much in the number, size and morphology of the chromosomes. The somatic chromosome number of the hybrid was found to be 2n= 16, consisting of two distinct genomes; the first set of six large chromosomes are probably derived from the gamete ofC. gigantea(2n=12), the male parent and the remaining 10 smaller chromosome from the gamete ofC. lacryma-jobivar.lacryma-jobi(2n= 20), the female parent. Meiotic studies of the hybrid showed mostly univalents, six of which are larger and 10 smaller ones. The hybrid showed total pollen and seed sterility because of the lack of homology between the chromosomes of the parents. It is suggested that these two species have diverged very early in evolution and are isolated by cytogenetic, geographical and ecological isolating mechanisms.