Extraction of the bark of Lunasia quercifolia (Warb.) Lauterb. & K. Schum., a species closely allied to Lunasia arnam, affords water-soluble bases (3-3.5%) which were shown to contain (-)-lunasine (I) as a major component. It has now been found that leaves of L. quercifolia contain about 1% quaternary bases composed partly of (-)-lunasine (I) but mainly of the (-)-O-methylluninium base (II), which may be regarded as derived from the known alkaloid (-)-lunine (III). Although (-)-O-methylluninium salts have not been isolated previously, R. Riegger and Stauffacher obtained (+)-O-methylluninium perchlorate as reaction product from the alkaloid (+)-lunidine (IV) isolated from a New Guinea species identified as Lunasia arnara Blanco var. repanda (Lauterb. & K. Schum) Lauterb. The structure of the (-)-O-methylluninium ion is readily deduced from comparison of its n.m.r. spectrum with that of lunasine and with the published spectra of lunine and lunacrine. Conversion of the iodide into the known tertiary base, (-)-lunine (III), confirmed the structural assignment based on spectroscopic data. The picrate and other (-)-O-methylluninium salts are converted in alkaline solution into a dextrorotatory, weakly basic substance, C₁₇H₂₁NO₅, the properties of which are in close agreement with those reported for (+)-lunidine (IV). Because of the ease with which this conversion takes place, the possibility remains that the alkaloid (+)-lunidine isolated by Riegger and Stauffacher may be an artefact. This suggestion is in accordance with the positive rotation reported for lunidine and the O-methylluninium salt derived from it.