1. The qualitative and quantitative composition of the combined alkaloids from the leaves, stems, seeds, and roots of Ammothamnus lehmanni Bge. according to its vegetation periods have been studied. 2. It has been found that the young plant contains predominantly the N-oxide forms of the matrine alkaloids, and as the plant develops these are reduced to the free bases. 3. A new base lehmannine, C15H22ON2 has been isolated for which 12,13-dehydromatrine is proposed as the most probable structure. © 1976 Plenum Publishing Corporation.