A new alkaloid, krigenamine (IX), has been isolated from Nerine krigeii, but neronine, previously isolated, is found to be absent from the plant itself. Krigenamine is shown to belong to the hemiacetal group of alkaloids by its several reactions, and is reduced to a base (VI) which is quaternised to falcatine methiodide (X) . The absolute structure is accordingly established and the aromatic oxygenation is identified with that of the pyrrolo[3,2,1-de]- phenanthridine base falcatine.