The alkaloid contents of Argemone hispida Gray and A. munita Dur. & Hilg. subsp. rotundata (Rydb.) G. B. Ownb. have been established and compared with other Argemone species in a search for biogenetic and chemotaxonomic relationships. A new alkaloid, munitagine, has been isolated from A. munita and its structure has been shown to be 2,7-dihydroxy-3,8-dimethoxy-5,6,11,12-tetrahydrodibenzo [a,e] cyclooctene-N-methyl-6,12-imine. This represents the first alkaloid of the dibenzocyclooctene group to exhibit an altered substituent pattern. [formula-ommitted] The structures of all alkaloids of this group, including munitagine, can be correlated with that of reticuline, which was found to occur in both species. © 1966, American Chemical Society. All rights reserved.