The study of the land plants was a part of the over-all program of the Laboratory of Radiation Biology. In this re- port only the results of this portion of the program are presented. The results of the investigations on organisms already have been reported: crabs (14) | invertebrates (8) , the following 2 reef fish | 4) land and algae (29) , The main objective of the land plant program was to determine the length of time required for a plant damaged by a nuclear detonation to resume its normal functions of growth and reproduction while being subjected to chronic radiation. Other objectives were to determine (1) the rate of decline of beta radioactivity in the tissues of land plants growing in radioactive soil during the period starting shortly after detonation of a nuclear device months later; (Nectar) and ending eigh=een (2) the gross beta radioactivity of the land plants at several islands of =niwetok Atoll, and take by the plants of specific radioisotopes from the soil. The main site of study was of the detonation (Fig. 1). Belle Island, (3) the up- 2.7 miles 3-SE This area was estimated to be far enough removed from ground zero that the plants would not be uprooted by physical forces yet would have taken up suf- ficient radioactivity for the proposed study. Other islands