1.- Seven species ofHeliotropiumfrom Karachi, West Pakistan, were studied cytologically to find out the possible trends of polyploid adaptation, as well as to provide data that could be used taxonomically.2.- Including previous cytological information, the genus showed a considerable variation in chromosome numbers. The haploid chromosome numbers were found to be n = 8, 12, 14, 16, 24 and 32. These aneuploids and polyploids occupy a different ecological condition than the diploid, extending apparently, to more recent habitats which are more severe.3.- Presence of multivalents as well as univalents inH. rariflorumwithn= 24 chromosomes indicates it to be a segmental allopolyploid.4.- The three morphologically similar speciesH. lignosum, H. tuberculosumandH. undulatum, possess a similar chromosome number ofn= 16. However,H. undulatumchromosomes differ in being smaller than the other two species