Wood anatomy of Argemone fruticosa, sole shrubby species of the genus, is distinctive in having growth rings, thick-walled libriform fibres, thick-walled ray cells with large intercellular spaces, vessels with grooves interconnecting pit apertures, and restriction of vessels to central portions of fascicular areas. Most of these features are related to the xeric ecology of this species. Argemone turnerae is an herbaceous perennial with large roots and sterns, the wood of which exhibits features distinctively related to this habit, including succulence (axial parenchyma substitutes for libriform fibres). Both species of Argemone share such features as storied wood structure and absence of uniseriate rays, which are infrequent in dicotyledons at large but common in other Papaveraceae. Wood data are not decisive in indicating whether the ancestors of Argemone or Papaveraceae were woody or herbaceous, but several features indicative of paedomorphosis can be found in the wood. Bark of Argemone is briefly described.