Corydalis incisa (Thunb.) Pers. has yielded three known alkaloids (protopine, adlumidine, and l-corypalmine) as well as one (F62) which has not been identified. The structures of adlumidine and of capnoidine have been determined as the same as that of bicuculline. They are optical antipodes and on admixture yield a racemic compound.