31 by Witkamp and Frank (1963). It may be possible to distinguish between translocation within the roots and downward movement along root channels at Rongelap by comparing the ratios of radionuclides within the roots and in the immediately surrounding soil in core sections. For example, if there is greater move- ment along root channels, we would expect sb??, which is not absorbed by the plants, to be most abundant in the soil adjacent to the roots at depth, if there is appreciable channelization. Pumice Radionuclides are also adsorbed by pumice particles. No detailed morphological examinations of the soil sections have been made, but it is obvious in some core sections that a few of the larger "hot spots" several inches below the surface are associated with pumice fragments. The retention of radionu- clides by pumice fragments may be of importance in considering soil-plant relationships in a few highly localized areas since proliferation of roots around pumice fragments has been observed (Sachet 1955; Kenady 1962). beneath the surface, However, as pumice is rarely found the effects of this material would not be generally important. We can not explain the differences in distribution of radionuclides between soil types but assume that the greater retention oe]