1. Ultracentrifuge pattern (59,800 rpm) of DNA-containing fraction obtained from Interspecific hybrid between Solamun demissuln x S. tuberosum 1506-b(9) (Genotype R_1R_4) and Norin No. 1 (Genotype r)showed S_<20.w.> =40.45S and 57.28S, S_<20.w.> =12.06S and 29.37S, respectively.
2. Placing of 1% solution of DNA-containing fraction from resistant Interspecific hybrid 1506-b(9) on susceptible Benimaru gave abundant hypersensitive flecks than any other more dilute concentration of DNA.
3. Washing within 10 minutes after placing the DNA-containing fraction from resistant interspecific hybrid 1506-b(9) on susceptible Benimaru, the appearance of hypersensitive flecks was checked easily.
4. Potato cuttings were placed on ^3H-thymidine solution (2μC/ml) for 4 days and DNA-containing fraction was obtained from these young leaves. Another potato cuttings were placed on 0.4% solution of the DNA-containing fraction. Microautoradiography was carried out on the tissues on which epidermis the DNA-containing fraction was placed or the apical tissues of leaves which were placed on the DNAcontaining fraction. Silver grains were recognized on these tissues and on the epidermal surface.
5. High radioactivity of ^3H-cytidine was observed on the plot treated with DNAcontaining fraction of other variety.