RADIO-LCOLOG\ =-1.367 foliage consistently has higher K but lower Cs in the upper than in the lower leaves. This would be in accord with a previous study (Rediske and Selders, 1953) which showed Cs to function as a relatively immobile element in bean plants. Data from additional field samples of a greater number of plant species are being accumulated at present with the hope of establishing more clearly the differences between species in this respect and the significance of the sharp differences between the older and youngerleaves. The K and Cs-137 contents of field-collected leachates from Rongelap soil have been shown to be greatest immediately following a dry period (Cole ct al., 1960). Since there are marked seasonal differences in precipitation at Rongelap Atoll this may have a bearing on some of the results which have been discussed. REFERENCES ro] Core, D. W., Gesset, S. P., and Herp, E. E. 1960. Tension lysimeter studies in glacial till and coral ‘atoll soils. Proc. Soil Sci. Soc. Amer. (in press). 2. jenny, H., Viasus, J., and Mantix, W. E. 1950. Hilgardia 20: 1-8. 3. Nisuita, H., Romney, E. M., ALExanper, G. V., and Larson, k. H. 1960. Soil Science 89: 167-76. oe . Repisxe, J. H. and Setpens, A. A. 1953. The uptake and translocation of cesium by plants. U.S. Atomic Energy Commission, Tech. Information Service, HW-35174. 19 pp. ;