1. Tumor Inhibitors. 105. For previous paper in the series, seeC. H. Lantz, J. G. Kalpaxis, J. Larner, R. M. Schubert andS. M. Kupchan, Biochem. Pharmac., in press.
2. J. L. Hartwell, Lloydia34, 386 (1971).
3. Thalli ofCladonia leptoclada were collected in New Zealand in June, 1965. We thankDr. Robert E. Perdue Jr., U.S. Department of Agriculture, Beltsville, Md., for supplying the plant material.
4. Tumor-inhibitory activity was assayed under the auspices of the National Cancer Institute as described byR. I. Geran, N. H. Greenberg, M. M. McDonald, A. M. Schumacher andB. J. Abbott, Cancer Chemother. Rep. part 3,3, 1 (1972).
5. W. Karrer,Konstitution und Vorkommen der organischen Pflanzenstoffe (Birkhäuser Verlag, Basel 1958), p. 710.