Rosmarinine, isolated originally from Senecio rosmarinifolius Linn., has now been found in other Senecio species. S. hygrophilus R. A. Dyer and C. A. Sm. is conspecific with " S. adnatus " DC.'of de Waal and Tiedt, who isolated platyphylline ; but the alkaloid content varies : rosmarinine, platyphylline, and an alkaloid C,8Hz,0,N, m. p. 176", have been isolated as sole constituents or as mixtures, depending on stage of growth, season and district.Senecic acid, found free in the plant and obtained by hydrolysis if platyphylline and.rosmarinine, is isolated as its open-chain form and as the monolactone. Rosmarinecine, now obtained crys alline, is assigned a structure (I1 or 111). The identity of platynecic acid and senecic acid is confirmed.