On the basis of alkaloidal, morphological and chromosomal studies, the section Mecones Bernh. (Syn.: Papaver L., sect. Papaver) has been subdivided into two sections. Thus the new section Glauca J. Novak includes the species Papaver glaucum Boiss. et Hausskn., P. gracile Auch. and P. decaisnei Hochst. et Steud., whereas the section mecones Bernh. only the species P. somniferum L. and P. setigerum Dc. The major alkaloids of the species of the section mecones are the morphinane alkaloids morphine and codeine, whereas those of the section Glauca the rhoeadine and the papaverrubines. The section mecones has the basic chromosome number x = 11, and the section Glauca x = 7. The basic chromosome numbers have been correlated with the morphological features.