differences in levels of activity but no obvious seasonal variations or changes with time. 5. The mobility of csi37 and sr?9 have an important bearing on sampling. Results of the 1958 collections and greenhouse tests indicated a marked difference in sr90, csi37, cium content of terminal and basal leaves. potassium and cal- Wherever possible the 1959 collections have included both terminal and basal leaves. csl37 moves into the terminal leaves more readily than sr?° and appears to be less mobile than potassium. Material has been col- lected but analyses remain to be done to determine possible effects of potassium content of the various soils in this regard. Fertili- zation plots and greenhouse tests indicate a depression of csi37 uptake with the addition of potassium. However, a similar depres- Sion has been observed with nitrogen and phosphorus amendments. 6. Wherever possible plant samples are taken in the immediate vicinity of the soil-plots. Certain trees have also been marked so that repeated collections can be made from the same individual. 7. In conjunction with the soils studies greenhouse tests have been conducted using Rongelap soils and various amendments. Ferti- lizer plots have been established in the field in both uncultivated and cultivated areas. alist, Mr. Niel Morriss, Trust Territory Agricultur- has been especially cooperative in establishing plots in a- 9002250