- 26 - reduction by a factor of 4.9. The fact that Belle Island was washed by the water wave from at least one other test device subsequent to the contamination by wi85 and Henry Island was not, may account for the greater reduction in activity on Scaevola leaves at Belle Island. Four species of algae collected at Belle Island on August 20 had high levels of wis as follows: Polysiphonia 1,100,000 d/m/g Spyridia 1,000,000 4/m/g Padina 910,000 d/m/g Halimeda 600,000 d/m/g The wi8s activity in the algae samples is related to the surface area-to-weight ratio in the four species. phonia and Spyridia are branching, Polysi- finely divided forms and have the greatest surface area per unit weight. Padina is flabellate with a smaller surface area and Halimeda is a heavyjointed calcareous form with the least surface area per unit weight. ‘he limited data available on the levels of w® in the above algae samples suggest that the contamination is present mainly on the surface, although a greater number of “samples would be necessary to show with certainty that this is the case. The levels of wi85 in the algae were higher than those in the land plants at the same island (Table 2).