~ 25 - yi85 accounted for 67 to 70 per cent of the total radioactivity in samples of Scaevola leaves taken at Belle Island on June 20, 1958 (Table 3). On August 20 the same isotope contributed 73 per cent of the total activity in a similar sample. The disintegration rates of the August 20 samples corrected to the June 20 date, however, indicate that wis would have contributed 66 per cent of the total radioactivity at that time, the percentage difference being due to the presence of more radioisotopes with a short half life in the earlier sample. June 23, In Scaevola leaves taken from Henry Island on wi85 contributed 17 per cent of the total activity. On August 20 the same isotope accounted for 11 per cent of the disintegration rate. When the August 20 disintegration rates were corrected to the June 23 date, 12 per cent of the total radioactivity. wi85 contributed Thus the rate of removal of this isotope from the Scaevola leaves by rain and wind is not significantly different from the average of the other radioisotopes. The disintegration rate of wi85 on Scaevola leaves at Belle Island on June 20 was 7,900,000 d/m/g and on August 20 180,000 d/m/g, a reduction in activity by a factor of 44. The disintegration rate of wi85 on Scaevola leaves at Henry Island on June 23 was 2,500 d/m/g and on August 20, 510 d/m/g, a